diff --git a/signpost.c b/signpost.c
index 05d4eaf..d4812a2 100644
--- a/signpost.c
+++ b/signpost.c
@@ -423,6 +423,8 @@ static char *validate_params(game_params *params, int full)
 {
     if (params->w < 2 || params->h < 2)
 	return "Width and height must both be at least two";
+    if (params->w == 2 && params->h == 2)   /* leads to generation hang */
+	return "Width and height cannot both be two";
 
     return NULL;
 }