diff --git a/protos/protos.cc b/protos/protos.cc
index fde6120a5a..db814f3603 100644
--- a/protos/protos.cc
+++ b/protos/protos.cc
@@ -20,6 +20,7 @@
 #include "upb/message/internal/extension.h"
 #include "upb/message/message.h"
 #include "upb/message/promote.h"
+#include "upb/message/value.h"
 #include "upb/mini_table/extension.h"
 #include "upb/mini_table/extension_registry.h"
 #include "upb/mini_table/message.h"
@@ -122,19 +123,12 @@ bool HasExtensionOrUnknown(const upb_Message* msg,
                  .status == kUpb_FindUnknown_Ok;
 }
 
-const upb_Extension* GetOrPromoteExtension(upb_Message* msg,
-                                           const upb_MiniTableExtension* eid,
-                                           upb_Arena* arena) {
+bool GetOrPromoteExtension(upb_Message* msg, const upb_MiniTableExtension* eid,
+                           upb_Arena* arena, upb_MessageValue* value) {
   MessageLock msg_lock(msg);
-  const upb_Extension* ext = UPB_PRIVATE(_upb_Message_Getext)(msg, eid);
-  if (ext == nullptr) {
-    upb_GetExtension_Status ext_status = upb_MiniTable_GetOrPromoteExtension(
-        (upb_Message*)msg, eid, 0, arena, &ext);
-    if (ext_status != kUpb_GetExtension_Ok) {
-      ext = nullptr;
-    }
-  }
-  return ext;
+  upb_GetExtension_Status ext_status = upb_Message_GetOrPromoteExtension(
+      (upb_Message*)msg, eid, 0, arena, value);
+  return ext_status == kUpb_GetExtension_Ok;
 }
 
 absl::StatusOr<absl::string_view> Serialize(const upb_Message* message,
diff --git a/protos/protos.h b/protos/protos.h
index db06de80fd..208d7c17fb 100644
--- a/protos/protos.h
+++ b/protos/protos.h
@@ -223,9 +223,8 @@ absl::StatusOr<absl::string_view> Serialize(const upb_Message* message,
 bool HasExtensionOrUnknown(const upb_Message* msg,
                            const upb_MiniTableExtension* eid);
 
-const upb_Extension* GetOrPromoteExtension(upb_Message* msg,
-                                           const upb_MiniTableExtension* eid,
-                                           upb_Arena* arena);
+bool GetOrPromoteExtension(upb_Message* msg, const upb_MiniTableExtension* eid,
+                           upb_Arena* arena, upb_MessageValue* value);
 
 void DeepCopy(upb_Message* target, const upb_Message* source,
               const upb_MiniTable* mini_table, upb_Arena* arena);
@@ -410,15 +409,16 @@ absl::StatusOr<Ptr<const Extension>> GetExtension(
     Ptr<T> message,
     const ::protos::internal::ExtensionIdentifier<Extendee, Extension>& id) {
   // TODO: Fix const correctness issues.
-  const upb_Extension* ext = ::protos::internal::GetOrPromoteExtension(
+  upb_MessageValue value;
+  const bool ok = ::protos::internal::GetOrPromoteExtension(
       const_cast<upb_Message*>(internal::GetInternalMsg(message)),
-      id.mini_table_ext(), ::protos::internal::GetArena(message));
-  if (!ext) {
+      id.mini_table_ext(), ::protos::internal::GetArena(message), &value);
+  if (!ok) {
     return ExtensionNotFoundError(
         upb_MiniTableExtension_Number(id.mini_table_ext()));
   }
   return Ptr<const Extension>(::protos::internal::CreateMessage<Extension>(
-      (upb_Message*)ext->data.ptr, ::protos::internal::GetArena(message)));
+      (upb_Message*)value.msg_val, ::protos::internal::GetArena(message)));
 }
 
 template <typename T, typename Extendee, typename Extension,
diff --git a/upb/message/promote.c b/upb/message/promote.c
index ef42159252..a1b0d0371c 100644
--- a/upb/message/promote.c
+++ b/upb/message/promote.c
@@ -64,12 +64,14 @@ static upb_UnknownToMessageRet upb_MiniTable_ParseUnknownMessage(
   return ret;
 }
 
-upb_GetExtension_Status upb_MiniTable_GetOrPromoteExtension(
+upb_GetExtension_Status upb_Message_GetOrPromoteExtension(
     upb_Message* msg, const upb_MiniTableExtension* ext_table,
-    int decode_options, upb_Arena* arena, const upb_Extension** extension) {
+    int decode_options, upb_Arena* arena, upb_MessageValue* value) {
   UPB_ASSERT(upb_MiniTableExtension_CType(ext_table) == kUpb_CType_Message);
-  *extension = UPB_PRIVATE(_upb_Message_Getext)(msg, ext_table);
-  if (*extension) {
+  const upb_Extension* extension =
+      UPB_PRIVATE(_upb_Message_Getext)(msg, ext_table);
+  if (extension) {
+    memcpy(value, &extension->data, sizeof(upb_MessageValue));
     return kUpb_GetExtension_Ok;
   }
 
@@ -104,8 +106,8 @@ upb_GetExtension_Status upb_MiniTable_GetOrPromoteExtension(
   if (!ext) {
     return kUpb_GetExtension_OutOfMemory;
   }
-  memcpy(&ext->data, &extension_msg, sizeof(extension_msg));
-  *extension = ext;
+  ext->data.ptr = extension_msg;
+  value->msg_val = extension_msg;
   const char* delete_ptr = upb_Message_GetUnknown(msg, &len) + ofs;
   upb_Message_DeleteUnknown(msg, delete_ptr, result.len);
   return kUpb_GetExtension_Ok;
diff --git a/upb/message/promote.h b/upb/message/promote.h
index 0a43f6bf70..c280c10268 100644
--- a/upb/message/promote.h
+++ b/upb/message/promote.h
@@ -33,14 +33,13 @@ typedef enum {
   kUpb_GetExtensionAsBytes_EncodeError,
 } upb_GetExtensionAsBytes_Status;
 
-// Returns a message extension or promotes an unknown field to
-// an extension.
+// Returns a message value or promotes an unknown field to an extension.
 //
 // TODO: Only supports extension fields that are messages,
 // expand support to include non-message types.
-upb_GetExtension_Status upb_MiniTable_GetOrPromoteExtension(
+upb_GetExtension_Status upb_Message_GetOrPromoteExtension(
     upb_Message* msg, const upb_MiniTableExtension* ext_table,
-    int decode_options, upb_Arena* arena, const upb_Extension** extension);
+    int decode_options, upb_Arena* arena, upb_MessageValue* value);
 
 typedef enum {
   kUpb_FindUnknown_Ok,
diff --git a/upb/message/promote_test.cc b/upb/message/promote_test.cc
index 3b79cb8b55..1dc8932e87 100644
--- a/upb/message/promote_test.cc
+++ b/upb/message/promote_test.cc
@@ -123,57 +123,57 @@ TEST(GeneratedCode, Extensions) {
   char* serialized =
       upb_test_ModelWithExtensions_serialize(msg, arena, &serialized_size);
 
-  const upb_Extension* upb_ext2;
   upb_test_ModelExtension1* ext1;
   upb_test_ModelExtension2* ext2;
   upb_GetExtension_Status promote_status;
+  upb_MessageValue value;
 
   // Test known GetExtension 1
-  promote_status = upb_MiniTable_GetOrPromoteExtension(
+  promote_status = upb_Message_GetOrPromoteExtension(
       UPB_UPCAST(msg), &upb_test_ModelExtension1_model_ext_ext, 0, arena,
-      &upb_ext2);
-  ext1 = (upb_test_ModelExtension1*)upb_ext2->data.ptr;
+      &value);
+  ext1 = (upb_test_ModelExtension1*)value.msg_val;
   EXPECT_EQ(kUpb_GetExtension_Ok, promote_status);
   EXPECT_TRUE(upb_StringView_IsEqual(upb_StringView_FromString("World"),
                                      upb_test_ModelExtension1_str(ext1)));
 
   // Test known GetExtension 2
-  promote_status = upb_MiniTable_GetOrPromoteExtension(
+  promote_status = upb_Message_GetOrPromoteExtension(
       UPB_UPCAST(msg), &upb_test_ModelExtension2_model_ext_ext, 0, arena,
-      &upb_ext2);
-  ext2 = (upb_test_ModelExtension2*)upb_ext2->data.ptr;
+      &value);
+  ext2 = (upb_test_ModelExtension2*)value.msg_val;
   EXPECT_EQ(kUpb_GetExtension_Ok, promote_status);
   EXPECT_EQ(5, upb_test_ModelExtension2_i(ext2));
 
   // Test known GetExtension 3
-  promote_status = upb_MiniTable_GetOrPromoteExtension(
+  promote_status = upb_Message_GetOrPromoteExtension(
       UPB_UPCAST(msg), &upb_test_ModelExtension2_model_ext_2_ext, 0, arena,
-      &upb_ext2);
-  ext2 = (upb_test_ModelExtension2*)upb_ext2->data.ptr;
+      &value);
+  ext2 = (upb_test_ModelExtension2*)value.msg_val;
   EXPECT_EQ(kUpb_GetExtension_Ok, promote_status);
   EXPECT_EQ(6, upb_test_ModelExtension2_i(ext2));
 
   // Test known GetExtension 4
-  promote_status = upb_MiniTable_GetOrPromoteExtension(
+  promote_status = upb_Message_GetOrPromoteExtension(
       UPB_UPCAST(msg), &upb_test_ModelExtension2_model_ext_3_ext, 0, arena,
-      &upb_ext2);
-  ext2 = (upb_test_ModelExtension2*)upb_ext2->data.ptr;
+      &value);
+  ext2 = (upb_test_ModelExtension2*)value.msg_val;
   EXPECT_EQ(kUpb_GetExtension_Ok, promote_status);
   EXPECT_EQ(7, upb_test_ModelExtension2_i(ext2));
 
   // Test known GetExtension 5
-  promote_status = upb_MiniTable_GetOrPromoteExtension(
+  promote_status = upb_Message_GetOrPromoteExtension(
       UPB_UPCAST(msg), &upb_test_ModelExtension2_model_ext_4_ext, 0, arena,
-      &upb_ext2);
-  ext2 = (upb_test_ModelExtension2*)upb_ext2->data.ptr;
+      &value);
+  ext2 = (upb_test_ModelExtension2*)value.msg_val;
   EXPECT_EQ(kUpb_GetExtension_Ok, promote_status);
   EXPECT_EQ(8, upb_test_ModelExtension2_i(ext2));
 
   // Test known GetExtension 6
-  promote_status = upb_MiniTable_GetOrPromoteExtension(
+  promote_status = upb_Message_GetOrPromoteExtension(
       UPB_UPCAST(msg), &upb_test_ModelExtension2_model_ext_5_ext, 0, arena,
-      &upb_ext2);
-  ext2 = (upb_test_ModelExtension2*)upb_ext2->data.ptr;
+      &value);
+  ext2 = (upb_test_ModelExtension2*)value.msg_val;
   EXPECT_EQ(kUpb_GetExtension_Ok, promote_status);
   EXPECT_EQ(9, upb_test_ModelExtension2_i(ext2));
 
@@ -188,51 +188,51 @@ TEST(GeneratedCode, Extensions) {
   EXPECT_EQ(0, upb_Message_ExtensionCount(UPB_UPCAST(base_msg)));
 
   // Test unknown GetExtension.
-  promote_status = upb_MiniTable_GetOrPromoteExtension(
+  promote_status = upb_Message_GetOrPromoteExtension(
       UPB_UPCAST(base_msg), &upb_test_ModelExtension1_model_ext_ext, 0, arena,
-      &upb_ext2);
-  ext1 = (upb_test_ModelExtension1*)upb_ext2->data.ptr;
+      &value);
+  ext1 = (upb_test_ModelExtension1*)value.msg_val;
   EXPECT_EQ(kUpb_GetExtension_Ok, promote_status);
   EXPECT_TRUE(upb_StringView_IsEqual(upb_StringView_FromString("World"),
                                      upb_test_ModelExtension1_str(ext1)));
 
   // Test unknown GetExtension.
-  promote_status = upb_MiniTable_GetOrPromoteExtension(
+  promote_status = upb_Message_GetOrPromoteExtension(
       UPB_UPCAST(base_msg), &upb_test_ModelExtension2_model_ext_ext, 0, arena,
-      &upb_ext2);
-  ext2 = (upb_test_ModelExtension2*)upb_ext2->data.ptr;
+      &value);
+  ext2 = (upb_test_ModelExtension2*)value.msg_val;
   EXPECT_EQ(kUpb_GetExtension_Ok, promote_status);
   EXPECT_EQ(5, upb_test_ModelExtension2_i(ext2));
 
   // Test unknown GetExtension.
-  promote_status = upb_MiniTable_GetOrPromoteExtension(
+  promote_status = upb_Message_GetOrPromoteExtension(
       UPB_UPCAST(base_msg), &upb_test_ModelExtension2_model_ext_2_ext, 0, arena,
-      &upb_ext2);
-  ext2 = (upb_test_ModelExtension2*)upb_ext2->data.ptr;
+      &value);
+  ext2 = (upb_test_ModelExtension2*)value.msg_val;
   EXPECT_EQ(kUpb_GetExtension_Ok, promote_status);
   EXPECT_EQ(6, upb_test_ModelExtension2_i(ext2));
 
   // Test unknown GetExtension.
-  promote_status = upb_MiniTable_GetOrPromoteExtension(
+  promote_status = upb_Message_GetOrPromoteExtension(
       UPB_UPCAST(base_msg), &upb_test_ModelExtension2_model_ext_3_ext, 0, arena,
-      &upb_ext2);
-  ext2 = (upb_test_ModelExtension2*)upb_ext2->data.ptr;
+      &value);
+  ext2 = (upb_test_ModelExtension2*)value.msg_val;
   EXPECT_EQ(kUpb_GetExtension_Ok, promote_status);
   EXPECT_EQ(7, upb_test_ModelExtension2_i(ext2));
 
   // Test unknown GetExtension.
-  promote_status = upb_MiniTable_GetOrPromoteExtension(
+  promote_status = upb_Message_GetOrPromoteExtension(
       UPB_UPCAST(base_msg), &upb_test_ModelExtension2_model_ext_4_ext, 0, arena,
-      &upb_ext2);
-  ext2 = (upb_test_ModelExtension2*)upb_ext2->data.ptr;
+      &value);
+  ext2 = (upb_test_ModelExtension2*)value.msg_val;
   EXPECT_EQ(kUpb_GetExtension_Ok, promote_status);
   EXPECT_EQ(8, upb_test_ModelExtension2_i(ext2));
 
   // Test unknown GetExtension.
-  promote_status = upb_MiniTable_GetOrPromoteExtension(
+  promote_status = upb_Message_GetOrPromoteExtension(
       UPB_UPCAST(base_msg), &upb_test_ModelExtension2_model_ext_5_ext, 0, arena,
-      &upb_ext2);
-  ext2 = (upb_test_ModelExtension2*)upb_ext2->data.ptr;
+      &value);
+  ext2 = (upb_test_ModelExtension2*)value.msg_val;
   EXPECT_EQ(kUpb_GetExtension_Ok, promote_status);
   EXPECT_EQ(9, upb_test_ModelExtension2_i(ext2));