diff --git a/image.c b/image.c
index 3fadd82ac..70e479a27 100644
--- a/image.c
+++ b/image.c
@@ -101,6 +101,18 @@ static const struct image_backend image_backend_sixel = {
 	sixel_free_output, sixel_geometry_changed
 };
 
+/* Compare images by server ID. */
+static int
+image_cmp(struct image *a, struct image *b)
+{
+	if (a->id < b->id)
+		return (-1);
+	if (a->id > b->id)
+		return (1);
+	return (0);
+}
+RB_GENERATE_STATIC(images, image, entry, image_cmp);
+
 /* Find the image backend supported by a terminal. */
 static const struct image_backend *
 image_tty_find_backend(struct tty *tty)
@@ -164,18 +176,6 @@ image_tty_free(struct tty *tty, int send)
 	tty->image_data = NULL;
 }
 
-/* Compare images by server ID. */
-static int
-image_cmp(struct image *a, struct image *b)
-{
-	if (a->id < b->id)
-		return (-1);
-	if (a->id > b->id)
-		return (1);
-	return (0);
-}
-RB_GENERATE_STATIC(images, image, entry, image_cmp);
-
 /* Average a rectangle of image pixels into one fallback sample. */
 static void
 image_sample(struct image *im, uint64_t sample_x, uint64_t sample_y,