diff --git a/openbox/screen.c b/openbox/screen.c
index ecffa487..0198c36c 100644
--- a/openbox/screen.c
+++ b/openbox/screen.c
@@ -1681,7 +1681,7 @@ guint screen_find_monitor(const Rect *search)
 {
     guint i;
     guint mostpx_index = screen_num_monitors;
-    guint mostpx = 0;
+    glong mostpx = 0;
     guint closest_distance_index = screen_num_monitors;
     guint closest_distance = G_MAXUINT;
     GSList *counted = NULL;