diff --git a/display.h b/display.h
index 341b1616c..5f99849b7 100644
--- a/display.h
+++ b/display.h
@@ -26,4 +26,6 @@ extern void plot(struct graphics_context *gc, cairo_rectangle_int_t *drawing_are
 extern void init_profile_background(struct graphics_context *gc);
 extern void attach_tooltip(int x, int y, int w, int h, const char *text);
 
+extern char zoomed_plot;
+
 #endif
diff --git a/gtk-gui.c b/gtk-gui.c
index f25fbaa53..9bd4f131d 100644
--- a/gtk-gui.c
+++ b/gtk-gui.c
@@ -24,7 +24,6 @@ GtkWidget *vpane, *hpane;
 GtkWidget *notebook;
 
 int        error_count;
-extern char zoomed_plot;
 
 const char *divelist_font;