diff --git a/calmwm.h b/calmwm.h
index faa8506..451e634 100644
--- a/calmwm.h
+++ b/calmwm.h
@@ -476,7 +476,6 @@ void			 search_print_text(struct menu *, int);
 void			 search_print_wm(struct menu *, int);
 
 struct region_ctx	*region_find(struct screen_ctx *, int, int);
-struct geom		 screen_apply_gap(struct screen_ctx *, struct geom);
 struct screen_ctx	*screen_find(Window);
 struct geom		 screen_area(struct screen_ctx *, int, int,
 			     enum apply_gap);
diff --git a/screen.c b/screen.c
index 5025899..0cb4ae0 100644
--- a/screen.c
+++ b/screen.c
@@ -31,6 +31,8 @@
 
 #include "calmwm.h"
 
+static struct geom screen_apply_gap(struct screen_ctx *, struct geom);
+
 void
 screen_init(int which)
 {
@@ -220,7 +222,7 @@ screen_update_geometry(struct screen_ctx *sc)
 	xu_ewmh_net_workarea(sc);
 }
 
-struct geom
+static struct geom
 screen_apply_gap(struct screen_ctx *sc, struct geom geom)
 {
 	geom.x += sc->gap.left;