1 files changed, 7 insertions, 1 deletions
diff --git a/python/google/protobuf/internal/type_checkers.py b/python/google/protobuf/internal/type_checkers.py
index 118725da..76c056c4 100755
--- a/python/google/protobuf/internal/type_checkers.py
+++ b/python/google/protobuf/internal/type_checkers.py
@@ -59,6 +59,8 @@ from google.protobuf import descriptor
 
 _FieldDescriptor = descriptor.FieldDescriptor
 
+def SupportsOpenEnums(field_descriptor):
+  return field_descriptor.containing_type.syntax == "proto3"
 
 def GetTypeChecker(field):
   """Returns a type checker for a message field of the specified types.
@@ -74,7 +76,11 @@ def GetTypeChecker(field):
       field.type == _FieldDescriptor.TYPE_STRING):
     return UnicodeValueChecker()
   if field.cpp_type == _FieldDescriptor.CPPTYPE_ENUM:
-    return EnumValueChecker(field.enum_type)
+    if SupportsOpenEnums(field):
+      # When open enums are supported, any int32 can be assigned.
+      return _VALUE_CHECKERS[_FieldDescriptor.CPPTYPE_INT32]
+    else:
+      return EnumValueChecker(field.enum_type)
   return _VALUE_CHECKERS[field.cpp_type]