diff --git a/tmux-image.h b/tmux-image.h
index 9616e739b..bb9735e0e 100644
--- a/tmux-image.h
+++ b/tmux-image.h
@@ -21,7 +21,7 @@
 #define TMUX_IMAGE_H
 
 #ifdef ENABLE_IMAGES
-//#error image support is not ready yet
+#error image support is not ready yet
 
 struct grid;
 struct grid_cell;