diff --git a/unix/gtkmain.c b/unix/gtkmain.c
index 751a80ff..a3cdb270 100644
--- a/unix/gtkmain.c
+++ b/unix/gtkmain.c
@@ -298,6 +298,17 @@ static void version(FILE *fp) {
 
 static const char *geometry_string;
 
+void cmdline_error(const char *p, ...)
+{
+    va_list ap;
+    fprintf(stderr, "%s: ", appname);
+    va_start(ap, p);
+    vfprintf(stderr, p, ap);
+    va_end(ap);
+    fputc('\n', stderr);
+    exit(1);
+}
+
 int do_cmdline(int argc, char **argv, int do_everything, int *allow_launch,
                Conf *conf)
 {
diff --git a/unix/gtkwin.c b/unix/gtkwin.c
index 418d6875..f0c3c3fb 100644
--- a/unix/gtkwin.c
+++ b/unix/gtkwin.c
@@ -3789,17 +3789,6 @@ void modalfatalbox(const char *p, ...)
     exit(1);
 }
 
-void cmdline_error(const char *p, ...)
-{
-    va_list ap;
-    fprintf(stderr, "%s: ", appname);
-    va_start(ap, p);
-    vfprintf(stderr, p, ap);
-    va_end(ap);
-    fputc('\n', stderr);
-    exit(1);
-}
-
 const char *get_x_display(void *frontend)
 {
     return gdk_get_display();