diff --git a/CHANGES.txt b/CHANGES.txt
index f5afcdf47c5c..b3c43613f18e 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -7,6 +7,10 @@
   * Fixed a data loss bug that could occur when the number of `optional`
     fields in a message is an exact multiple of 32. (#9440).
 
+  PHP
+  * Fixed a data loss bug that could occur when the number of `optional`
+    fields in a message is an exact multiple of 32. (#9440).
+    
 2022-01-10 version 3.19.3 (C++/Java/Python/PHP/Objective-C/C#/Ruby/JavaScript)
 
   Python
diff --git a/php/ext/google/protobuf/php-upb.c b/php/ext/google/protobuf/php-upb.c
index a668fe0c6d5c..925faa645a56 100644
--- a/php/ext/google/protobuf/php-upb.c
+++ b/php/ext/google/protobuf/php-upb.c
@@ -5968,7 +5968,7 @@ static void make_layout(symtab_addctx *ctx, const upb_msgdef *m) {
   }
 
   /* Account for space used by hasbits. */
-  l->size = div_round_up(hasbit, 8);
+  l->size = div_round_up(hasbit + 1, 8);
 
   /* Allocate non-oneof fields. */
   for (upb_msg_field_begin(&it, m); !upb_msg_field_done(&it);
diff --git a/php/tests/GeneratedClassTest.php b/php/tests/GeneratedClassTest.php
index 837f05215ddc..a6101dcbfb2b 100644
--- a/php/tests/GeneratedClassTest.php
+++ b/php/tests/GeneratedClassTest.php
@@ -9,6 +9,7 @@
 use Bar\TestLegacyMessage;
 use Bar\TestLegacyMessage_NestedEnum;
 use Bar\TestLegacyMessage_NestedMessage;
+use Foo\Test32Fields;
 use Foo\TestEnum;
 use Foo\TestIncludeNamespaceMessage;
 use Foo\TestIncludePrefixMessage;
@@ -1849,4 +1850,13 @@ public function testNoExceptionWithVarDump()
 
         $this->assertTrue(true);
     }
+
+    public function testIssue9440()
+    {
+        $m = new Test32Fields();
+        $m->setId(8);
+        $this->assertEquals(8, $m->getId());
+        $m->setVersion('1');
+        $this->assertEquals(8, $m->getId());
+    }
 }
diff --git a/php/tests/proto/test.proto b/php/tests/proto/test.proto
index 609b8cfe0cdc..421292ab5287 100644
--- a/php/tests/proto/test.proto
+++ b/php/tests/proto/test.proto
@@ -306,3 +306,38 @@ message TestBytesValue {
     int32 int32_field = 4;
   }
 }
+
+message Test32Fields {
+  optional uint32 id = 1;
+  optional uint32 random_name_a0 = 2;
+  optional uint32 random_name_a1 = 3;
+  optional uint32 random_name_a2 = 4;
+  optional uint32 random_name_a3 = 5;
+  optional uint32 random_name_a4 = 6;
+  optional uint32 random_name_a5 = 7;
+  optional uint32 random_name_a6 = 8;
+  optional uint32 random_name_a7 = 9;
+  optional uint32 random_name_a8 = 10;
+  optional uint32 random_name_a9 = 11;
+  optional uint32 random_name_b0 = 12;
+  optional uint32 random_name_b1 = 13;
+  optional uint32 random_name_b2 = 14;
+  optional uint32 random_name_b3 = 15;
+  optional uint32 random_name_b4 = 16;
+  optional uint32 random_name_b5 = 17;
+  optional uint32 random_name_b6 = 18;
+  optional uint32 random_name_b7 = 19;
+  optional uint32 random_name_b8 = 20;
+  optional uint32 random_name_b9 = 21;
+  optional uint32 random_name_c0 = 22;
+  optional uint32 random_name_c1 = 23;
+  optional uint32 random_name_c2 = 24;
+  optional uint32 random_name_c3 = 25;
+  optional uint32 random_name_c4 = 26;
+  optional uint32 random_name_c5 = 27;
+  optional uint32 random_name_c6 = 28;
+  optional uint32 random_name_c7 = 29;
+  optional uint32 random_name_c8 = 30;
+  optional uint32 random_name_c9 = 31;
+  optional string version = 32;
+}