diff --git a/python/google/protobuf/pyext/unknown_fields.h b/python/google/protobuf/pyext/unknown_fields.h
index a26195513e..94d55e148d 100755
--- a/python/google/protobuf/pyext/unknown_fields.h
+++ b/python/google/protobuf/pyext/unknown_fields.h
@@ -34,7 +34,6 @@
 #include <Python.h>
 
 #include <memory>
-#include <hash_map>
 #include <set>
 
 #include <google/protobuf/pyext/message.h>