diff --git a/ocaml/boot/menhir/parser.ml b/ocaml/boot/menhir/parser.ml
index 7350b9b6ef6..eb61b720129 100644
--- a/ocaml/boot/menhir/parser.ml
+++ b/ocaml/boot/menhir/parser.ml
@@ -1166,7 +1166,7 @@ end = struct
 
   let assert_unboxed_literals ~loc =
     Language_extension.(
-      Jane_syntax_parsing.assert_extension_enabled ~loc Layouts Beta)
+      Jane_syntax_parsing.assert_extension_enabled ~loc Layouts Alpha)
 
   let unboxed ~loc x =
     assert_unboxed_literals ~loc:(make_loc loc);
diff --git a/ocaml/lambda/matching.ml b/ocaml/lambda/matching.ml
index f74f3abf4d7..9a5cf59384d 100644
--- a/ocaml/lambda/matching.ml
+++ b/ocaml/lambda/matching.ml
@@ -1171,6 +1171,7 @@ let can_group discr pat =
   | Constant (Const_char _), Constant (Const_char _)
   | Constant (Const_string _), Constant (Const_string _)
   | Constant (Const_float _), Constant (Const_float _)
+  | Constant (Const_unboxed_float _), Constant (Const_unboxed_float _)
   | Constant (Const_int32 _), Constant (Const_int32 _)
   | Constant (Const_int64 _), Constant (Const_int64 _)
   | Constant (Const_nativeint _), Constant (Const_nativeint _) ->
@@ -1194,7 +1195,7 @@ let can_group discr pat =
       ( Any
       | Constant
           ( Const_int _ | Const_char _ | Const_string _ | Const_float _
-          | Const_int32 _ | Const_int64 _ | Const_nativeint _ )
+          | Const_unboxed_float _ | Const_int32 _ | Const_int64 _ | Const_nativeint _ )
       | Construct _ | Tuple _ | Record _ | Array _ | Variant _ | Lazy ) ) ->
       false
 
@@ -2536,7 +2537,7 @@ let rec do_tests_fail value_kind loc fail tst arg = function
   | [] -> fail
   | (c, act) :: rem ->
       Lifthenelse
-        ( Lprim (tst, [ arg; Lconst (Const_base c) ], loc),
+        ( Lprim (tst, [ arg; c ], loc),
           do_tests_fail value_kind loc fail tst arg rem,
           act, value_kind )
 
@@ -2545,15 +2546,16 @@ let rec do_tests_nofail value_kind loc tst arg = function
   | [ (_, act) ] -> act
   | (c, act) :: rem ->
       Lifthenelse
-        ( Lprim (tst, [ arg; Lconst (Const_base c) ], loc),
+        ( Lprim (tst, [ arg; c ], loc),
           do_tests_nofail value_kind loc tst arg rem,
           act, value_kind )
 
-let make_test_sequence value_kind loc fail tst lt_tst arg const_lambda_list =
+let make_test_sequence value_kind loc fail tst lt_tst arg const_lambda_list transl_const =
   let const_lambda_list = sort_lambda_list const_lambda_list in
   let hs, const_lambda_list, fail =
     share_actions_tree value_kind const_lambda_list fail
   in
+  let const_lambda_list = List.map (fun (c, l) -> transl_const c, l) const_lambda_list in
   let rec make_test_sequence const_lambda_list =
     if List.length const_lambda_list >= 4 && lt_tst <> Pignore then
       split_sequence const_lambda_list
@@ -2566,7 +2568,7 @@ let make_test_sequence value_kind loc fail tst lt_tst arg const_lambda_list =
       rev_split_at (List.length const_lambda_list / 2) const_lambda_list
     in
     Lifthenelse
-      ( Lprim (lt_tst, [ arg; Lconst (Const_base (fst (List.hd list2))) ], loc),
+      ( Lprim (lt_tst, [ arg; fst (List.hd list2) ], loc),
         make_test_sequence list1,
         make_test_sequence list2, value_kind )
   in
@@ -2963,6 +2965,16 @@ let mk_failaction_pos partial seen ctx defs =
 let combine_constant value_kind loc arg cst partial ctx def
     (const_lambda_list, total, _pats) =
   let fail, local_jumps = mk_failaction_neg partial ctx def in
+  let transl_const = function
+  | Const_int c -> Lconst(Const_base (Const_int c))
+  | Const_char c -> Lconst(Const_base (Const_char c))
+  | Const_string (s,loc,d) -> Lconst(Const_base (Const_string (s,loc,d)))
+  | Const_float c -> Lconst(Const_base (Const_float c))
+  | Const_int32 c -> Lconst(Const_base (Const_int32 c))
+  | Const_int64 c -> Lconst(Const_base (Const_int64 c))
+  | Const_nativeint c -> Lconst(Const_base (Const_nativeint c))
+  | Const_unboxed_float f -> Lconst (Const_base (Const_float f))
+  in
   let lambda1 =
     match cst with
     | Const_int _ ->
@@ -3002,22 +3014,28 @@ let combine_constant value_kind loc arg cst partial ctx def
     | Const_float _ ->
         make_test_sequence value_kind loc fail (Pfloatcomp CFneq)
           (Pfloatcomp CFlt) arg
-          const_lambda_list
+          const_lambda_list transl_const
+    | Const_unboxed_float _ ->
+        make_test_sequence value_kind loc fail
+          (Pfloatcomp CFneq)
+          (Pfloatcomp CFlt)
+          (Lprim (Pbox_float Lambda.alloc_local, [arg], loc))
+          const_lambda_list transl_const
     | Const_int32 _ ->
         make_test_sequence value_kind loc fail
           (Pbintcomp (Pint32, Cne))
           (Pbintcomp (Pint32, Clt))
-          arg const_lambda_list
+          arg const_lambda_list transl_const
     | Const_int64 _ ->
         make_test_sequence value_kind loc fail
           (Pbintcomp (Pint64, Cne))
           (Pbintcomp (Pint64, Clt))
-          arg const_lambda_list
+          arg const_lambda_list transl_const
     | Const_nativeint _ ->
         make_test_sequence value_kind loc fail
           (Pbintcomp (Pnativeint, Cne))
           (Pbintcomp (Pnativeint, Clt))
-          arg const_lambda_list
+          arg const_lambda_list transl_const
   in
   (lambda1, Jumps.union local_jumps total)
 
diff --git a/ocaml/lambda/translcore.ml b/ocaml/lambda/translcore.ml
index 6a84c44d9e8..c5ae7452213 100644
--- a/ocaml/lambda/translcore.ml
+++ b/ocaml/lambda/translcore.ml
@@ -390,7 +390,18 @@ and transl_exp0 ~in_new_scope ~scopes sort e =
       transl_ident (of_location ~scopes e.exp_loc)
         e.exp_env e.exp_type path desc kind
   | Texp_constant cst ->
-      Lconst(Const_base cst)
+    begin match cst with
+    | Const_int c -> Lconst(Const_base (Const_int c))
+    | Const_char c -> Lconst(Const_base (Const_char c))
+    | Const_string (s,loc,d) -> Lconst(Const_base (Const_string (s,loc,d)))
+    | Const_float c -> Lconst(Const_base (Const_float c))
+    | Const_int32 c -> Lconst(Const_base (Const_int32 c))
+    | Const_int64 c -> Lconst(Const_base (Const_int64 c))
+    | Const_nativeint c -> Lconst(Const_base (Const_nativeint c))
+    | Const_unboxed_float f ->
+      Lprim (Punbox_float, [Lconst (Const_base (Const_float f))],
+        of_location ~scopes e.exp_loc)
+    end
   | Texp_let(rec_flag, pat_expr_list, body) ->
       let return_layout = layout_exp sort body in
       transl_let ~scopes ~return_layout rec_flag pat_expr_list
diff --git a/ocaml/parsing/parser.mly b/ocaml/parsing/parser.mly
index 6468bd06495..470d7bd9728 100644
--- a/ocaml/parsing/parser.mly
+++ b/ocaml/parsing/parser.mly
@@ -941,7 +941,7 @@ end = struct
 
   let assert_unboxed_literals ~loc =
     Language_extension.(
-      Jane_syntax_parsing.assert_extension_enabled ~loc Layouts Beta)
+      Jane_syntax_parsing.assert_extension_enabled ~loc Layouts Alpha)
 
   let unboxed ~loc x =
     assert_unboxed_literals ~loc:(make_loc loc);
diff --git a/ocaml/testsuite/tests/typing-layouts-float64/alloc.ml b/ocaml/testsuite/tests/typing-layouts-float64/alloc.ml
index 3587110852b..5252eb85930 100644
--- a/ocaml/testsuite/tests/typing-layouts-float64/alloc.ml
+++ b/ocaml/testsuite/tests/typing-layouts-float64/alloc.ml
@@ -1,6 +1,6 @@
 (* TEST
    * flambda2
-   flags = "-extension layouts_beta"
+   flags = "-extension layouts_alpha"
    ** native
 *)
 
@@ -167,3 +167,18 @@ let _ =
   let _ = measure_alloc_value (fun () -> cse_test false r) in
   let allocs = get_exact_allocations () in
   Printf.printf "CSE test (0 bytes):\n  allocated bytes: %.2f\n" allocs
+
+let[@inline never] literal_test x y =
+  let open Float_u in
+  (#1. + x) * (y - #4.) / (#3. ** #1.)
+
+let print_allocs s =
+  let allocs = get_exact_allocations () in
+  Printf.printf
+    "%s:\n  allocated bytes: %.2f\n"
+    s allocs
+
+let _ =
+  let r = measure_alloc (fun () -> literal_test #2. #3.) in
+  assert (Float_u.equal r (-#1.));
+  print_allocs "Float literals";
diff --git a/ocaml/testsuite/tests/typing-layouts-float64/alloc.reference b/ocaml/testsuite/tests/typing-layouts-float64/alloc.reference
index 8cd7f847e22..23a3a02bf88 100644
--- a/ocaml/testsuite/tests/typing-layouts-float64/alloc.reference
+++ b/ocaml/testsuite/tests/typing-layouts-float64/alloc.reference
@@ -18,3 +18,5 @@ Manipulation (0 bytes):
   d: 45.14
 CSE test (0 bytes):
   allocated bytes: 0.00
+Float literals:
+  allocated bytes: 0.00
diff --git a/ocaml/testsuite/tests/typing-layouts/literals.ml b/ocaml/testsuite/tests/typing-layouts/literals.ml
index 125c9b9890c..bb9541234c1 100644
--- a/ocaml/testsuite/tests/typing-layouts/literals.ml
+++ b/ocaml/testsuite/tests/typing-layouts/literals.ml
@@ -3,87 +3,70 @@
    * expect
 *)
 
+(*****************************************)
+(* Prelude: Functions on unboxed floats. *)
+
+module Float_u = Stdlib__Float_u
+
+let test s f = Format.printf "%s: %f\n" s (Float_u.to_float f); Format.print_flush ()
+
+[%%expect{|
+module Float_u = Stdlib__Float_u
+val test : string -> float# -> unit = <fun>
+|}]
+
 (*****************************************)
 (* Expressions *)
 
-let e = #2.718281828459045
+let () = test "e" #2.718281828459045
+
 [%%expect{|
-Line 1, characters 8-26:
-1 | let e = #2.718281828459045
-            ^^^^^^^^^^^^^^^^^^
-Error: Unboxed float literals aren't supported yet.
+e: 2.718282
 |}]
 
-let negative_one_half = -#0.5
+let () = test "negative_one_half" (-#0.5)
 [%%expect{|
-Line 1, characters 24-29:
-1 | let negative_one_half = -#0.5
-                            ^^^^^
-Error: Unboxed float literals aren't supported yet.
+negative_one_half: -0.500000
 |}]
 
-let negative_one_half = - #0.5
+let () = test "negative_one_half" (- #0.5)
 [%%expect{|
-Line 1, characters 24-30:
-1 | let negative_one_half = - #0.5
-                            ^^^^^^
-Error: Unboxed float literals aren't supported yet.
+negative_one_half: -0.500000
 |}]
 
-let negative_one_half = -.#0.5
+let () = test "negative_one_half" (-.#0.5)
 [%%expect{|
-Line 1, characters 24-30:
-1 | let negative_one_half = -.#0.5
-                            ^^^^^^
-Error: Unboxed float literals aren't supported yet.
+negative_one_half: -0.500000
 |}]
 
-let negative_one_half = -. #0.5
+let () = test "negative_one_half" (-. #0.5)
 [%%expect{|
-Line 1, characters 24-31:
-1 | let negative_one_half = -. #0.5
-                            ^^^^^^^
-Error: Unboxed float literals aren't supported yet.
+negative_one_half: -0.500000
 |}]
 
-let positive_one_dot = +#1.
+let () = test "positive_one_dot" (+#1.)
 [%%expect{|
-Line 1, characters 23-27:
-1 | let positive_one_dot = +#1.
-                           ^^^^
-Error: Unboxed float literals aren't supported yet.
+positive_one_dot: 1.000000
 |}]
 
-let positive_one_dot = + #1.
+let () = test "positive_one_dot" (+ #1.)
 [%%expect{|
-Line 1, characters 23-28:
-1 | let positive_one_dot = + #1.
-                           ^^^^^
-Error: Unboxed float literals aren't supported yet.
+positive_one_dot: 1.000000
 |}]
 
-let positive_one_dot = +.#1.
+let () = test "positive_one_dot" (+.#1.)
 [%%expect{|
-Line 1, characters 23-28:
-1 | let positive_one_dot = +.#1.
-                           ^^^^^
-Error: Unboxed float literals aren't supported yet.
+positive_one_dot: 1.000000
 |}]
 
-let positive_one_dot = +. #1.
+let () = test "positive_one_dot" (+. #1.)
 [%%expect{|
-Line 1, characters 23-29:
-1 | let positive_one_dot = +. #1.
-                           ^^^^^^
-Error: Unboxed float literals aren't supported yet.
+positive_one_dot: 1.000000
 |}]
 
-let one_billion = #1e9
+let () = test "one_billion" (#1e9)
 [%%expect{|
-Line 1, characters 18-22:
-1 | let one_billion = #1e9
-                      ^^^^
-Error: Unboxed float literals aren't supported yet.
+one_billion: 1000000000.000000
 |}]
 
 let zero = #0n
@@ -150,28 +133,22 @@ Line 1, characters 26-36:
 Error: Unboxed int literals aren't supported yet.
 |}]
 
-let one_twenty_seven_point_two_five_in_floating_hex = #0x7f.4
+let () = test "one_twenty_seven_point_two_five_in_floating_hex" (#0x7f.4)
 [%%expect{|
-Line 1, characters 54-61:
-1 | let one_twenty_seven_point_two_five_in_floating_hex = #0x7f.4
-                                                          ^^^^^^^
-Error: Unboxed float literals aren't supported yet.
+one_twenty_seven_point_two_five_in_floating_hex: 127.250000
 |}]
 
-let five_point_three_seven_five_in_floating_hexponent = #0xa.cp-1
+let () = test "five_point_three_seven_five_in_floating_hexponent" (#0xa.cp-1)
 [%%expect{|
-Line 1, characters 56-65:
-1 | let five_point_three_seven_five_in_floating_hexponent = #0xa.cp-1
-                                                            ^^^^^^^^^
-Error: Unboxed float literals aren't supported yet.
+five_point_three_seven_five_in_floating_hexponent: 5.375000
 |}]
 
-let unknown_floating_point_suffix = #0.P
+let () = test "unknown_floating_point_suffix" (#0.P)
 [%%expect{|
-Line 1, characters 36-40:
-1 | let unknown_floating_point_suffix = #0.P
-                                        ^^^^
-Error: Unboxed float literals aren't supported yet.
+Line 1, characters 46-52:
+1 | let () = test "unknown_floating_point_suffix" (#0.P)
+                                                  ^^^^^^
+Error: Unknown modifier 'P' for literal #0.P
 |}]
 
 (*****************************************)
@@ -201,17 +178,51 @@ let f x =
 
 f #5.;;
 [%%expect {|
-Line 3, characters 4-7:
-3 |   | #4. -> `Four
-        ^^^
-Error: Unboxed float literals aren't supported yet.
+val f : float# -> [> `Five | `Four | `Other ] = <fun>
+- : [> `Five | `Four | `Other ] = `Five
+|}];;
+
+let f x =
+  match x with
+  | #4. -> #0.
+  | #5. -> #1.
+  | x ->  x
+;;
+
+test "result" (f #7.);;
+[%%expect {|
+val f : float# -> float# = <fun>
+result: 7.000000
+- : unit = ()
 |}];;
 
+let f x =
+  match x with
+  | #4. -> #0.
+  | #5. -> #1.
+;;
+
+test "result" (f #7.);;
+(* This is here to test the [partial-match] warning *)
+[%%expect {|
+Lines 2-4, characters 2-14:
+2 | ..match x with
+3 |   | #4. -> #0.
+4 |   | #5. -> #1.
+Warning 8 [partial-match]: this pattern-matching is not exhaustive.
+Here is an example of a case that is not matched:
+#0.
+
+val f : float# -> float# = <fun>
+Exception: Match_failure ("", 2, 2).
+|}];;
+
+
 (*****************************************)
 (* Lexing edge cases *)
 
 (* Unboxed literals at the beginning of the line aren't directives. *)
-let f _ _ = ();;
+let f (_ : float#) _ = ();;
 let () = f
 #2.
 #2L
@@ -222,13 +233,14 @@ let () = f
 ;;
 
 [%%expect{|
-val f : 'a -> 'b -> unit = <fun>
-Line 3, characters 0-3:
-3 | #2.
+val f : float# -> 'a -> unit = <fun>
+Line 4, characters 0-3:
+4 | #2L
     ^^^
-Error: Unboxed float literals aren't supported yet.
+Error: Unboxed int literals aren't supported yet.
 |}];;
 
+let f _ _ = ();;
 let () = f
 (* This lexes as a directive. #2 is not a valid unboxed int literal
    anyway, as it lacks a suffix.
@@ -239,4 +251,5 @@ let () = f
 ;;
 
 [%%expect{|
+val f : 'a -> 'b -> unit = <fun>
 |}];;
diff --git a/ocaml/testsuite/tests/typing-layouts/literals_native.ml b/ocaml/testsuite/tests/typing-layouts/literals_native.ml
new file mode 100644
index 00000000000..a59fcbdd62b
--- /dev/null
+++ b/ocaml/testsuite/tests/typing-layouts/literals_native.ml
@@ -0,0 +1,61 @@
+(* TEST
+   flags = "-extension layouts_alpha"
+   * native
+   * bytecode
+*)
+
+(*****************************************)
+(* Prelude: Functions on unboxed floats. *)
+
+module Float_u = struct
+  include Stdlib__Float_u
+
+  let ( + ) = add
+  let ( - ) = sub
+  let ( * ) = mul
+  let ( / ) = div
+  let ( ** ) = pow
+  let ( > ) x y = (compare x y) > 0
+end
+
+let test s f = Format.printf "%s: %f\n%!" s (Float_u.to_float f)
+
+(*****************************************)
+(* Expressions *)
+
+let () = test "e" #2.718281828459045
+let () = test "negative_one_half" (-#0.5)
+let () = test "negative_one_half" (- #0.5)
+let () = test "negative_one_half" (-.#0.5)
+let () = test "negative_one_half" (-. #0.5)
+let () = test "positive_one_dot" (+#1.)
+let () = test "positive_one_dot" (+ #1.)
+let () = test "positive_one_dot" (+.#1.)
+let () = test "positive_one_dot" (+. #1.)
+let () = test "one_billion" (#1e9)
+let () = test "one_twenty_seven_point_two_five_in_floating_hex" (#0x7f.4)
+let () = test "five_point_three_seven_five_in_floating_hexponent" (#0xa.cp-1)
+
+(*****************************************)
+(* Patterns *)
+
+let f x =
+  match x with
+  | #4. -> `Four
+  | #5. -> `Five
+  | _ -> `Other
+;;
+
+let () =
+  match f #5. with
+  | `Five -> ()
+  | _ -> assert false;;
+
+let f x =
+  match x with
+  | #4. -> #0.
+  | #5. -> #1.
+  | x ->  x
+;;
+
+test "result" (f #7.);;
diff --git a/ocaml/testsuite/tests/typing-layouts/literals_native.reference b/ocaml/testsuite/tests/typing-layouts/literals_native.reference
new file mode 100644
index 00000000000..153a1973dd3
--- /dev/null
+++ b/ocaml/testsuite/tests/typing-layouts/literals_native.reference
@@ -0,0 +1,13 @@
+e: 2.718282
+negative_one_half: -0.500000
+negative_one_half: -0.500000
+negative_one_half: -0.500000
+negative_one_half: -0.500000
+positive_one_dot: 1.000000
+positive_one_dot: 1.000000
+positive_one_dot: 1.000000
+positive_one_dot: 1.000000
+one_billion: 1000000000.000000
+one_twenty_seven_point_two_five_in_floating_hex: 127.250000
+five_point_three_seven_five_in_floating_hexponent: 5.375000
+result: 7.000000
diff --git a/ocaml/typing/parmatch.ml b/ocaml/typing/parmatch.ml
index 1346b6e95ca..c77dd63991a 100644
--- a/ocaml/typing/parmatch.ml
+++ b/ocaml/typing/parmatch.ml
@@ -131,6 +131,7 @@ let all_coherent column =
         | Const_int64 _, Const_int64 _
         | Const_nativeint _, Const_nativeint _
         | Const_float _, Const_float _
+        | Const_unboxed_float _, Const_unboxed_float _
         | Const_string _, Const_string _ -> true
         | ( Const_char _
           | Const_int _
@@ -138,6 +139,7 @@ let all_coherent column =
           | Const_int64 _
           | Const_nativeint _
           | Const_float _
+          | Const_unboxed_float _
           | Const_string _), _ -> false
       end
     | Tuple l1, Tuple l2 -> l1 = l2
@@ -240,6 +242,7 @@ let is_absent_pat d =
 
 let const_compare x y =
   match x,y with
+  | Const_unboxed_float f1, Const_unboxed_float f2
   | Const_float f1, Const_float f2 ->
       Stdlib.compare (float_of_string f1) (float_of_string f2)
   | Const_string (s1, _, _), Const_string (s2, _, _) ->
@@ -248,6 +251,7 @@ let const_compare x y =
     |Const_char _
     |Const_string (_, _, _)
     |Const_float _
+    |Const_unboxed_float _
     |Const_int32 _
     |Const_int64 _
     |Const_nativeint _
@@ -1044,6 +1048,12 @@ let build_other ext env =
                     | _ -> assert false)
             (function f -> Tpat_constant(Const_float (string_of_float f)))
             0.0 (fun f -> f +. 1.0) d env
+      | Constant Const_unboxed_float _ ->
+          build_other_constant
+            (function Constant(Const_unboxed_float f) -> float_of_string f
+                    | _ -> assert false)
+            (function f -> Tpat_constant(Const_unboxed_float (string_of_float f)))
+            0.0 (fun f -> f +. 1.0) d env
       | Array (am, arg_sort, _) ->
           let all_lengths =
             List.map
@@ -2074,7 +2084,7 @@ let inactive ~partial pat =
         | Tpat_constant c -> begin
             match c with
             | Const_string _
-            | Const_int _ | Const_char _ | Const_float _
+            | Const_int _ | Const_char _ | Const_float _ | Const_unboxed_float _
             | Const_int32 _ | Const_int64 _ | Const_nativeint _ -> true
           end
         | Tpat_tuple ps | Tpat_construct (_, _, ps, _)
diff --git a/ocaml/typing/printpat.ml b/ocaml/typing/printpat.ml
index 846de53c87a..aaebd504a2d 100644
--- a/ocaml/typing/printpat.ml
+++ b/ocaml/typing/printpat.ml
@@ -29,6 +29,14 @@ let pretty_const c = match c with
 | Const_char c -> Printf.sprintf "%C" c
 | Const_string (s, _, _) -> Printf.sprintf "%S" s
 | Const_float f -> Printf.sprintf "%s" f
+| Const_unboxed_float f ->
+  let s =
+    match String.split_on_char '-' f with
+    | [""; f] -> "-#" ^ f
+    | [f] -> "#" ^ f
+    | _ -> assert false
+  in
+  Printf.sprintf "%s" s
 | Const_int32 i -> Printf.sprintf "%ldl" i
 | Const_int64 i -> Printf.sprintf "%LdL" i
 | Const_nativeint i -> Printf.sprintf "%ndn" i
diff --git a/ocaml/typing/printpat.mli b/ocaml/typing/printpat.mli
index 1865a2ab298..7334f588ce6 100644
--- a/ocaml/typing/printpat.mli
+++ b/ocaml/typing/printpat.mli
@@ -16,7 +16,7 @@
 
 
 val pretty_const
-    : Asttypes.constant -> string
+    : Typedtree.constant -> string
 val top_pretty
     : Format.formatter -> 'k Typedtree.general_pattern -> unit
 val pretty_pat
diff --git a/ocaml/typing/printtyped.ml b/ocaml/typing/printtyped.ml
index 4202676fbb2..b9cfbdf2503 100644
--- a/ocaml/typing/printtyped.ml
+++ b/ocaml/typing/printtyped.ml
@@ -67,6 +67,7 @@ let fmt_constant f x =
   | Const_string (s, strloc, Some delim) ->
       fprintf f "Const_string (%S,%a,Some %S)" s fmt_location strloc delim
   | Const_float (s) -> fprintf f "Const_float %s" s
+  | Const_unboxed_float (s) -> fprintf f "Const_unboxed_float %s" s
   | Const_int32 (i) -> fprintf f "Const_int32 %ld" i
   | Const_int64 (i) -> fprintf f "Const_int64 %Ld" i
   | Const_nativeint (i) -> fprintf f "Const_nativeint %nd" i
diff --git a/ocaml/typing/typecore.ml b/ocaml/typing/typecore.ml
index 527e75b90ee..ebb54d2b800 100644
--- a/ocaml/typing/typecore.ml
+++ b/ocaml/typing/typecore.ml
@@ -201,7 +201,6 @@ type error =
   | Exclave_in_nontail_position
   | Exclave_returns_not_local
   | Unboxed_int_literals_not_supported
-  | Unboxed_float_literals_not_supported
   | Function_type_not_rep of type_expr * Jkind.Violation.t
 
 exception Error of Location.t * Env.t * error
@@ -589,22 +588,17 @@ let optimise_allocations () =
 
 (* Typing of constants *)
 
-let type_constant = function
+let type_constant: Typedtree.constant -> type_expr = function
     Const_int _ -> instance Predef.type_int
   | Const_char _ -> instance Predef.type_char
   | Const_string _ -> instance Predef.type_string
   | Const_float _ -> instance Predef.type_float
+  | Const_unboxed_float _ -> instance Predef.type_unboxed_float
   | Const_int32 _ -> instance Predef.type_int32
   | Const_int64 _ -> instance Predef.type_int64
   | Const_nativeint _ -> instance Predef.type_nativeint
 
-let type_constant_unboxed env loc
-    : Jane_syntax.Layouts.constant -> _ = function
-  | Float _ -> raise (Error (loc, env, Unboxed_float_literals_not_supported))
-    (* CR layouts v2.5: This should be [instance Predef.type_unboxed_float] *)
-  | Integer _ -> raise (Error (loc, env, Unboxed_int_literals_not_supported))
-
-let constant_integer i ~suffix : (Asttypes.constant, error) result =
+let constant_integer i ~suffix : (Typedtree.constant, error) result =
   match suffix with
   | 'l' ->
     begin
@@ -623,7 +617,7 @@ let constant_integer i ~suffix : (Asttypes.constant, error) result =
     end
   | c -> Error (Unknown_literal (i, c))
 
-let constant : Parsetree.constant -> (Asttypes.constant, error) result =
+let constant : Parsetree.constant -> (Typedtree.constant, error) result =
   function
   | Pconst_integer (i, Some suffix) -> constant_integer i ~suffix
   | Pconst_integer (i,None) ->
@@ -641,22 +635,15 @@ let constant_or_raise env loc cst =
   | Ok c -> c
   | Error err -> raise (Error (loc, env, err))
 
-let unboxed_constant :
-    type a. Jane_syntax.Layouts.constant -> (a, error) result
+let unboxed_constant : Jane_syntax.Layouts.constant -> (Typedtree.constant, error) result
   = function
-  | Float (_, None) -> Error Unboxed_float_literals_not_supported
+  | Float (f, None) -> Ok (Const_unboxed_float f)
   | Float (x, Some c) -> Error (Unknown_literal ("#" ^ x, c))
   | Integer (_, _) -> Error Unboxed_int_literals_not_supported
 
-(* CR layouts v2.5: this is missing the part where we actually typecheck
-   unboxed literals.
-*)
 let unboxed_constant_or_raise env loc cst =
-  let open struct
-    type nothing = |
-  end in
   match unboxed_constant cst with
-  | Ok (_ : nothing) -> .
+  | Ok c -> c
   | Error err -> raise (Error (loc, env, err))
 
 (* Specific version of type_option, using newty rather than newgenty *)
@@ -2307,11 +2294,11 @@ and type_pat_aux
       | Jpat_immutable_array (Iapat_immutable_array spl) ->
           type_pat_array Immutable spl attrs
       | Jpat_layout (Lpat_constant cst) ->
-          let desc = unboxed_constant_or_raise !env loc cst in
+          let cst = unboxed_constant_or_raise !env loc cst in
           rvp @@ solve_expected {
-            pat_desc = desc;
+            pat_desc = Tpat_constant cst;
             pat_loc = loc; pat_extra=[];
-            pat_type = type_constant_unboxed !env loc cst;
+            pat_type = type_constant cst;
             pat_attributes = attrs;
             pat_env = !env }
     end
@@ -3021,7 +3008,11 @@ let rec check_counter_example_pat
       end
   | Tpat_alias (p, _, _, _, _) -> check_rec ~info p expected_ty k
   | Tpat_constant cst ->
-      let cst = constant_or_raise !env loc (Untypeast.constant cst) in
+      let cst =
+        match Untypeast.constant cst with
+        | `Parsetree cst -> constant_or_raise !env loc cst
+        | `Jane_syntax cst -> unboxed_constant_or_raise !env loc cst
+      in
       k @@ solve_expected (mp (Tpat_constant cst) ~pat_type:(type_constant cst))
   | Tpat_tuple tpl ->
       let tpl_ann =
@@ -8343,11 +8334,12 @@ and type_jkind_expr
       name (Some jkind_annot) sbody
 
 and type_unboxed_constant ~loc ~env ~rue ~attributes cst =
+  let cst = unboxed_constant_or_raise env loc cst in
   rue {
-    exp_desc = unboxed_constant_or_raise env loc cst;
+    exp_desc = Texp_constant cst;
     exp_loc = loc;
     exp_extra = [];
-    exp_type = type_constant_unboxed env loc cst;
+    exp_type = type_constant cst;
     exp_attributes = attributes;
     exp_env = env }
 
@@ -9274,9 +9266,6 @@ let report_error ~loc env = function
   | Unboxed_int_literals_not_supported ->
       Location.errorf ~loc
         "@[Unboxed int literals aren't supported yet.@]"
-  | Unboxed_float_literals_not_supported ->
-      Location.errorf ~loc
-        "@[Unboxed float literals aren't supported yet.@]"
   | Function_type_not_rep (ty,violation) ->
       Location.errorf ~loc
         "@[Function arguments and returns must be representable.@]@ %a"
diff --git a/ocaml/typing/typecore.mli b/ocaml/typing/typecore.mli
index dc2416ef24d..01b62aa0ba0 100644
--- a/ocaml/typing/typecore.mli
+++ b/ocaml/typing/typecore.mli
@@ -282,7 +282,6 @@ type error =
   | Exclave_in_nontail_position
   | Exclave_returns_not_local
   | Unboxed_int_literals_not_supported
-  | Unboxed_float_literals_not_supported
   | Function_type_not_rep of type_expr * Jkind.Violation.t
 
 exception Error of Location.t * Env.t * error
@@ -312,7 +311,7 @@ val type_package:
   (Env.t -> Parsetree.module_expr -> Path.t -> (Longident.t * type_expr) list ->
   Typedtree.module_expr * (Longident.t * type_expr) list) ref
 
-val constant: Parsetree.constant -> (Asttypes.constant, error) result
+val constant: Parsetree.constant -> (Typedtree.constant, error) result
 
 val check_recursive_bindings : Env.t -> Typedtree.value_binding list -> unit
 val check_recursive_class_bindings :
diff --git a/ocaml/typing/typedtree.ml b/ocaml/typing/typedtree.ml
index e7a600ef614..7518a5d1af2 100644
--- a/ocaml/typing/typedtree.ml
+++ b/ocaml/typing/typedtree.ml
@@ -18,6 +18,16 @@
 open Asttypes
 open Types
 
+type constant =
+    Const_int of int
+  | Const_char of char
+  | Const_string of string * Location.t * string option
+  | Const_float of string
+  | Const_unboxed_float of string
+  | Const_int32 of int32
+  | Const_int64 of int64
+  | Const_nativeint of nativeint
+
 module Uid = Shape.Uid
 
 (* Value expressions for the core language *)
diff --git a/ocaml/typing/typedtree.mli b/ocaml/typing/typedtree.mli
index 95162da0c9f..c816d216615 100644
--- a/ocaml/typing/typedtree.mli
+++ b/ocaml/typing/typedtree.mli
@@ -23,6 +23,20 @@
 
 open Asttypes
 
+(* We define a new constant type that can represent unboxed values.
+   This is currently used only in [Typedtree], but the long term goal
+   is to share this definition with [Lambda] and completely replace the
+   usage of [Asttypes.constant] *)
+type constant =
+    Const_int of int
+  | Const_char of char
+  | Const_string of string * Location.t * string option
+  | Const_float of string
+  | Const_unboxed_float of string
+  | Const_int32 of int32
+  | Const_int64 of int64
+  | Const_nativeint of nativeint
+
 module Uid = Shape.Uid
 
 (* Value expressions for the core language *)
diff --git a/ocaml/typing/untypeast.ml b/ocaml/typing/untypeast.ml
index 3cf255df765..3d8817853fa 100644
--- a/ocaml/typing/untypeast.ml
+++ b/ocaml/typing/untypeast.ml
@@ -131,13 +131,14 @@ let rec extract_letop_patterns n pat =
 (** Mapping functions. *)
 
 let constant = function
-  | Const_char c -> Pconst_char c
-  | Const_string (s,loc,d) -> Pconst_string (s,loc,d)
-  | Const_int i -> Pconst_integer (Int.to_string i, None)
-  | Const_int32 i -> Pconst_integer (Int32.to_string i, Some 'l')
-  | Const_int64 i -> Pconst_integer (Int64.to_string i, Some 'L')
-  | Const_nativeint i -> Pconst_integer (Nativeint.to_string i, Some 'n')
-  | Const_float f -> Pconst_float (f,None)
+  | Const_char c -> `Parsetree (Pconst_char c)
+  | Const_string (s,loc,d) -> `Parsetree (Pconst_string (s,loc,d))
+  | Const_int i -> `Parsetree (Pconst_integer (Int.to_string i, None))
+  | Const_int32 i -> `Parsetree (Pconst_integer (Int32.to_string i, Some 'l'))
+  | Const_int64 i -> `Parsetree (Pconst_integer (Int64.to_string i, Some 'L'))
+  | Const_nativeint i -> `Parsetree (Pconst_integer (Nativeint.to_string i, Some 'n'))
+  | Const_float f -> `Parsetree (Pconst_float (f,None))
+  | Const_unboxed_float f -> `Jane_syntax (Jane_syntax.Layouts.Float (f, None))
 
 let attribute sub a = {
     attr_name = map_loc sub a.attr_name;
@@ -358,7 +359,12 @@ let pattern : type k . _ -> k T.general_pattern -> _ = fun sub pat ->
 
     | Tpat_alias (pat, _id, name, _uid, _mode) ->
         Ppat_alias (sub.pat sub pat, name)
-    | Tpat_constant cst -> Ppat_constant (constant cst)
+    | Tpat_constant cst ->
+      begin match constant cst with
+      | `Parsetree cst -> Ppat_constant cst
+      | `Jane_syntax cst ->
+        Jane_syntax.Layouts.pat_of ~loc (Lpat_constant cst) |> add_jane_syntax_attributes
+      end
     | Tpat_tuple list ->
         Ppat_tuple (List.map (sub.pat sub) list)
     | Tpat_construct (lid, _, args, vto) ->
@@ -494,7 +500,12 @@ let expression sub exp =
   let desc =
     match exp.exp_desc with
       Texp_ident (_path, lid, _, _, _) -> Pexp_ident (map_loc sub lid)
-    | Texp_constant cst -> Pexp_constant (constant cst)
+    | Texp_constant cst ->
+      begin match constant cst with
+      | `Parsetree cst -> Pexp_constant cst
+      | `Jane_syntax cst ->
+        Jane_syntax.Layouts.expr_of ~loc (Lexp_constant cst) |> add_jane_syntax_attributes
+      end
     | Texp_let (rec_flag, list, exp) ->
         Pexp_let (rec_flag,
           List.map (sub.value_binding sub) list,
diff --git a/ocaml/typing/untypeast.mli b/ocaml/typing/untypeast.mli
index 809df9ad086..f4999384124 100644
--- a/ocaml/typing/untypeast.mli
+++ b/ocaml/typing/untypeast.mli
@@ -84,4 +84,5 @@ val untype_signature : ?mapper:mapper -> Typedtree.signature -> signature
 val untype_expression : ?mapper:mapper -> Typedtree.expression -> expression
 val untype_pattern : ?mapper:mapper -> _ Typedtree.general_pattern -> pattern
 
-val constant : Asttypes.constant -> Parsetree.constant
+val constant : Typedtree.constant ->
+  [ `Parsetree of Parsetree.constant | `Jane_syntax of Jane_syntax.Layouts.constant ]