diff --git a/src/window.c b/src/window.c
index b2f01f6..1f5e709 100644
--- a/src/window.c
+++ b/src/window.c
@@ -64,7 +64,7 @@
 
 static win_T *win_alloc(win_T *after, int hidden);
 
-#define NOWIN		(win_T *)-1	// non-existing window
+#define NOWIN		((win_T *)-1)	// non-existing window
 
 #define ROWS_AVAIL (Rows - p_ch - tabline_height())