diff --git a/src/include/access/parallel.h b/src/include/access/parallel.h
index f4db882..5561cf8 100644
--- a/src/include/access/parallel.h
+++ b/src/include/access/parallel.h
@@ -52,7 +52,7 @@ typedef struct ParallelWorkerContext
 } ParallelWorkerContext;
 
 extern volatile bool ParallelMessagePending;
-extern int	ParallelWorkerNumber;
+extern PGDLLIMPORT int	ParallelWorkerNumber;
 extern bool InitializingParallelWorker;
 
 #define		IsParallelWorker()		(ParallelWorkerNumber >= 0)