diff --git a/python/extension_dict.c b/python/extension_dict.c
index bb58603815..c2bd4d6572 100644
--- a/python/extension_dict.c
+++ b/python/extension_dict.c
@@ -88,24 +88,9 @@ static void PyUpb_ExtensionDict_Dealloc(PyUpb_ExtensionDict* self) {
   PyUpb_Dealloc(self);
 }
 
-static const upb_fielddef* PyUpb_ExtensionDict_GetExtensionDef(PyObject* key) {
-  const upb_fielddef* f = PyUpb_FieldDescriptor_GetDef(key);
-  if (!f) {
-    PyErr_Clear();
-    PyErr_Format(PyExc_KeyError, "Object %R is not a field descriptor\n", key);
-    return NULL;
-  }
-  if (!upb_fielddef_isextension(f)) {
-    PyErr_Format(PyExc_KeyError, "Field %s is not an extension\n",
-                 upb_fielddef_fullname(f));
-    return NULL;
-  }
-  return f;
-}
-
 static int PyUpb_ExtensionDict_Contains(PyObject* _self, PyObject* key) {
   PyUpb_ExtensionDict* self = (PyUpb_ExtensionDict*)_self;
-  const upb_fielddef* f = PyUpb_ExtensionDict_GetExtensionDef(key);
+  const upb_fielddef* f = PyUpb_CMessage_GetExtensionDef(self->msg, key);
   if (!f) return -1;
   upb_msg* msg = PyUpb_CMessage_GetIfReified(self->msg);
   if (!msg) return 0;
@@ -125,7 +110,7 @@ static Py_ssize_t PyUpb_ExtensionDict_Length(PyObject* _self) {
 
 static PyObject* PyUpb_ExtensionDict_Subscript(PyObject* _self, PyObject* key) {
   PyUpb_ExtensionDict* self = (PyUpb_ExtensionDict*)_self;
-  const upb_fielddef* f = PyUpb_ExtensionDict_GetExtensionDef(key);
+  const upb_fielddef* f = PyUpb_CMessage_GetExtensionDef(self->msg, key);
   if (!f) return NULL;
   return PyUpb_CMessage_GetFieldValue(self->msg, f);
 }
@@ -133,7 +118,7 @@ static PyObject* PyUpb_ExtensionDict_Subscript(PyObject* _self, PyObject* key) {
 static int PyUpb_ExtensionDict_AssignSubscript(PyObject* _self, PyObject* key,
                                                PyObject* val) {
   PyUpb_ExtensionDict* self = (PyUpb_ExtensionDict*)_self;
-  const upb_fielddef* f = PyUpb_ExtensionDict_GetExtensionDef(key);
+  const upb_fielddef* f = PyUpb_CMessage_GetExtensionDef(self->msg, key);
   if (!f) return -1;
   if (val) {
     return PyUpb_CMessage_SetFieldValue(self->msg, f, val);
diff --git a/python/message.c b/python/message.c
index 7a3c8f6254..736358c29e 100644
--- a/python/message.c
+++ b/python/message.c
@@ -1068,13 +1068,8 @@ void PyUpb_CMessage_DoClearField(PyObject* _self, const upb_fielddef* f) {
 static PyObject* PyUpb_CMessage_ClearExtension(PyObject* _self, PyObject* arg) {
   PyUpb_CMessage* self = (void*)_self;
   PyUpb_CMessage_AssureReified(self);
-  const upb_msgdef* msgdef = _PyUpb_CMessage_GetMsgdef(self);
-  const upb_fielddef* f = PyUpb_FieldDescriptor_GetDef(arg);
+  const upb_fielddef* f = PyUpb_CMessage_GetExtensionDef(_self, arg);
   if (!f) return NULL;
-  if (upb_fielddef_containingtype(f) != msgdef) {
-    PyErr_Format(PyExc_ValueError, "Extension doesn't match (%s vs %s)",
-                 upb_msgdef_fullname(msgdef), upb_fielddef_fullname(f));
-  }
   PyUpb_CMessage_DoClearField(_self, f);
   Py_RETURN_NONE;
 }
@@ -1159,11 +1154,38 @@ err:
   goto done;
 }
 
+const upb_fielddef* PyUpb_CMessage_GetExtensionDef(PyObject* _self, PyObject* key) {
+  const upb_fielddef* f = PyUpb_FieldDescriptor_GetDef(key);
+  if (!f) {
+    PyErr_Clear();
+    PyErr_Format(PyExc_KeyError, "Object %R is not a field descriptor\n", key);
+    return NULL;
+  }
+  if (!upb_fielddef_isextension(f)) {
+    PyErr_Format(PyExc_KeyError, "Field %s is not an extension\n",
+                 upb_fielddef_fullname(f));
+    return NULL;
+  }
+  const upb_msgdef* msgdef = PyUpb_CMessage_GetMsgdef(_self);
+  if (upb_fielddef_containingtype(f) != msgdef) {
+    PyErr_Format(PyExc_KeyError, "Extension doesn't match (%s vs %s)",
+                 upb_msgdef_fullname(msgdef), upb_fielddef_fullname(f));
+    return NULL;
+  }
+  return f;
+}
+
+
 static PyObject* PyUpb_CMessage_HasExtension(PyObject* _self,
                                              PyObject* ext_desc) {
   upb_msg* msg = PyUpb_CMessage_GetIfReified(_self);
-  const upb_fielddef* f = PyUpb_FieldDescriptor_GetDef(ext_desc);
+  const upb_fielddef* f = PyUpb_CMessage_GetExtensionDef(_self, ext_desc);
   if (!f) return NULL;
+  if (upb_fielddef_isseq(f)) {
+    PyErr_SetString(PyExc_KeyError,
+                    "Field is repeated. A singular method is required.");
+    return NULL;
+  }
   if (!msg) Py_RETURN_FALSE;
   return PyBool_FromLong(upb_msg_has(msg, f));
 }
diff --git a/python/message.h b/python/message.h
index 3c4474743d..f67bf63ffc 100644
--- a/python/message.h
+++ b/python/message.h
@@ -69,6 +69,11 @@ PyObject* PyUpb_CMessage_SerializeToString(PyObject* self, PyObject* args,
 int PyUpb_CMessage_InitAttributes(PyObject* _self, PyObject* args,
                                   PyObject* kwargs);
 
+// Checks that `key` is a field descriptor for an extension type, and that the
+// extendee is this message.  Otherwise returns NULL and sets a KeyError.
+const upb_fielddef* PyUpb_CMessage_GetExtensionDef(PyObject* _self,
+                                                   PyObject* key);
+
 // Clears the given field in this message.
 void PyUpb_CMessage_DoClearField(PyObject* _self, const upb_fielddef* f);
 
diff --git a/python/pb_unit_tests/reflection_test_wrapper.py b/python/pb_unit_tests/reflection_test_wrapper.py
index ae9470d90b..e8a5d802e1 100644
--- a/python/pb_unit_tests/reflection_test_wrapper.py
+++ b/python/pb_unit_tests/reflection_test_wrapper.py
@@ -26,8 +26,6 @@
 from google.protobuf.internal import reflection_test
 import unittest
 
-#reflection_test.Proto2ReflectionTest.testExtensionDelete.__unittest_expecting_failure__ = True
-reflection_test.Proto2ReflectionTest.testExtensionFailureModes.__unittest_expecting_failure__ = True
 reflection_test.Proto2ReflectionTest.testExtensionIter.__unittest_expecting_failure__ = True
 reflection_test.Proto2ReflectionTest.testIsInitialized.__unittest_expecting_failure__ = True
 reflection_test.Proto2ReflectionTest.testListFieldsAndExtensions.__unittest_expecting_failure__ = True