diff --git a/nsprpub/pr/include/md/_unixos.h b/nsprpub/pr/include/md/_unixos.h
index 1a0352d70953..1b6f91cc4641 100644
--- a/nsprpub/pr/include/md/_unixos.h
+++ b/nsprpub/pr/include/md/_unixos.h
@@ -455,7 +455,7 @@ struct _MDFileMap {
 extern PRStatus _MD_CreateFileMap(struct PRFileMap *fmap, PRInt64 size);
 #define _MD_CREATE_FILE_MAP _MD_CreateFileMap
 
-#define _MD_GET_MEM_MAP_ALIGNMENT PR_GetPageSize()
+#define _MD_GET_MEM_MAP_ALIGNMENT() PR_GetPageSize()
 
 extern void * _MD_MemMap(struct PRFileMap *fmap, PRInt64 offset,
         PRUint32 len);