diff --git a/src/include/miscadmin.h b/src/include/miscadmin.h
index c2b786e..3807955 100644
--- a/src/include/miscadmin.h
+++ b/src/include/miscadmin.h
@@ -134,7 +134,7 @@ extern pid_t PostmasterPid;
 extern bool IsPostmasterEnvironment;
 extern PGDLLIMPORT bool IsUnderPostmaster;
 extern bool IsBackgroundWorker;
-extern bool IsBinaryUpgrade;
+extern PGDLLIMPORT bool IsBinaryUpgrade;
 
 extern bool ExitOnAnyError;