diff --git a/src/include/access/parallel.h b/src/include/access/parallel.h
index dffe891ce61..f8e467f2916 100644
--- a/src/include/access/parallel.h
+++ b/src/include/access/parallel.h
@@ -47,8 +47,8 @@ typedef struct ParallelContext
 } ParallelContext;
 
 extern volatile bool ParallelMessagePending;
-extern int	ParallelWorkerNumber;
-extern bool InitializingParallelWorker;
+extern PGDLLIMPORT int ParallelWorkerNumber;
+extern PGDLLIMPORT bool InitializingParallelWorker;
 
 #define		IsParallelWorker()		(ParallelWorkerNumber >= 0)