# https://github.com/protocolbuffers/protobuf/issues/21021
diff --git a/upb/mini_table/extension_registry.c b/upb/mini_table/extension_registry.c
index 65ac78732..ff33ec5fc 100644
--- a/upb/mini_table/extension_registry.c
+++ b/upb/mini_table/extension_registry.c
@@ -72,7 +72,7 @@ failure:
 
 #ifdef UPB_LINKARR_DECLARE
 
-UPB_LINKARR_DECLARE(upb_AllExts, upb_MiniTableExtension);
+UPB_LINKARR_DECLARE(upb_AllExts, const upb_MiniTableExtension);
 
 bool upb_ExtensionRegistry_AddAllLinkedExtensions(upb_ExtensionRegistry* r) {
   const upb_MiniTableExtension* start = UPB_LINKARR_START(upb_AllExts);