diff --git a/compiler/crates/relay-typegen/src/visit.rs b/compiler/crates/relay-typegen/src/visit.rs
index 857f3890acd29..0521391c665ff 100644
--- a/compiler/crates/relay-typegen/src/visit.rs
+++ b/compiler/crates/relay-typegen/src/visit.rs
@@ -1543,7 +1543,14 @@ fn make_prop(
                     if linked_field.node_type.is_list() {
                         AST::RawType(intern!("[]"))
                     } else {
-                        AST::RawType(intern!("null | void"))
+                        let typegen_language =
+                            typegen_context.project_config.typegen_config.language;
+
+                        if typegen_language == TypegenLanguage::TypeScript {
+                            AST::RawType(intern!("null | undefined"))
+                        } else {
+                            AST::RawType(intern!("null | void"))
+                        }
                     }
                 } else {
                     let setter_parameter = AST::Union(
diff --git a/compiler/crates/relay-typegen/tests/generate_typescript/fixtures/updatable-operation-assignable-fragment-plural.expected b/compiler/crates/relay-typegen/tests/generate_typescript/fixtures/updatable-operation-assignable-fragment-plural.expected
index 0c32fcd40b0c5..f2eb8c4391e4a 100644
--- a/compiler/crates/relay-typegen/tests/generate_typescript/fixtures/updatable-operation-assignable-fragment-plural.expected
+++ b/compiler/crates/relay-typegen/tests/generate_typescript/fixtures/updatable-operation-assignable-fragment-plural.expected
@@ -30,7 +30,7 @@ export type UpdatableQuery$data = {
     // value in case none of the concrete values match.
     readonly __typename: "%other";
   } | null;
-  set node(value: null | void);
+  set node(value: null | undefined);
 };
 export type UpdatableQuery = {
   response: UpdatableQuery$data;
diff --git a/compiler/crates/relay-typegen/tests/generate_typescript/fixtures/updatable-operation-assignable-fragments-within-narrowing.expected b/compiler/crates/relay-typegen/tests/generate_typescript/fixtures/updatable-operation-assignable-fragments-within-narrowing.expected
index 7fd56e290a157..4fc63abd12f7f 100644
--- a/compiler/crates/relay-typegen/tests/generate_typescript/fixtures/updatable-operation-assignable-fragments-within-narrowing.expected
+++ b/compiler/crates/relay-typegen/tests/generate_typescript/fixtures/updatable-operation-assignable-fragments-within-narrowing.expected
@@ -45,7 +45,7 @@ export type UpdatableQuery$data = {
       readonly " $fragmentSpreads": "Assignable_user";
     } | null);
   } | null;
-  set me(value: null | void);
+  set me(value: null | undefined);
 };
 export type UpdatableQuery = {
   response: UpdatableQuery$data;
diff --git a/compiler/crates/relay-typegen/tests/generate_typescript/fixtures/updatable-operation-multiple-assignable-fragments.expected b/compiler/crates/relay-typegen/tests/generate_typescript/fixtures/updatable-operation-multiple-assignable-fragments.expected
index d61f64269d1ae..6da7b354dae32 100644
--- a/compiler/crates/relay-typegen/tests/generate_typescript/fixtures/updatable-operation-multiple-assignable-fragments.expected
+++ b/compiler/crates/relay-typegen/tests/generate_typescript/fixtures/updatable-operation-multiple-assignable-fragments.expected
@@ -36,7 +36,7 @@ export type UpdatableQuery$data = {
       readonly " $fragmentSpreads": "Assignable_node";
     } | null);
   } | null;
-  set me(value: null | void);
+  set me(value: null | undefined);
 };
 export type UpdatableQuery = {
   response: UpdatableQuery$data;
diff --git a/compiler/crates/relay-typegen/tests/generate_typescript/fixtures/updatable-operation-special-fields.expected b/compiler/crates/relay-typegen/tests/generate_typescript/fixtures/updatable-operation-special-fields.expected
index fdd3893e6a778..2d2d7e5ea0f8c 100644
--- a/compiler/crates/relay-typegen/tests/generate_typescript/fixtures/updatable-operation-special-fields.expected
+++ b/compiler/crates/relay-typegen/tests/generate_typescript/fixtures/updatable-operation-special-fields.expected
@@ -20,7 +20,7 @@ export type UpdatableQuery$data = {
     readonly aliased_typename: "User";
     readonly id: string;
   } | null;
-  set me(value: null | void);
+  set me(value: null | undefined);
 };
 export type UpdatableQuery = {
   response: UpdatableQuery$data;
diff --git a/compiler/crates/relay-typegen/tests/generate_typescript/fixtures/updatable-operation-type-refinement.expected b/compiler/crates/relay-typegen/tests/generate_typescript/fixtures/updatable-operation-type-refinement.expected
index df7e57550e734..c3cafea523182 100644
--- a/compiler/crates/relay-typegen/tests/generate_typescript/fixtures/updatable-operation-type-refinement.expected
+++ b/compiler/crates/relay-typegen/tests/generate_typescript/fixtures/updatable-operation-type-refinement.expected
@@ -26,13 +26,13 @@ export type UpdatableQuery$data = {
     get address(): {
       city: string | null;
     } | null;
-    set address(value: null | void);
+    set address(value: null | undefined);
   } | {
     // This will never be '%other', but we need some
     // value in case none of the concrete values match.
     readonly __typename: "%other";
   } | null;
-  set maybeNodeInterface(value: null | void);
+  set maybeNodeInterface(value: null | undefined);
 };
 export type UpdatableQuery = {
   response: UpdatableQuery$data;
diff --git a/compiler/crates/relay-typegen/tests/generate_typescript/fixtures/updatable-operation.expected b/compiler/crates/relay-typegen/tests/generate_typescript/fixtures/updatable-operation.expected
index d8a05f586f7a6..6f1e7bdc23f12 100644
--- a/compiler/crates/relay-typegen/tests/generate_typescript/fixtures/updatable-operation.expected
+++ b/compiler/crates/relay-typegen/tests/generate_typescript/fixtures/updatable-operation.expected
@@ -12,7 +12,7 @@ export type UpdatableQuery$data = {
     actorCount: number | null;
     name: string | null;
   } | null;
-  set me(value: null | void);
+  set me(value: null | undefined);
 };
 export type UpdatableQuery = {
   response: UpdatableQuery$data;