diff --git a/samegame.c b/samegame.c
index 3597e19..3abd042 100644
--- a/samegame.c
+++ b/samegame.c
@@ -67,6 +67,7 @@
 #include <string.h>
 #include <assert.h>
 #include <ctype.h>
+#include <limits.h>
 #include <math.h>
 
 #include "puzzles.h"
@@ -285,6 +286,8 @@ static const char *validate_params(const game_params *params, bool full)
 {
     if (params->w < 1 || params->h < 1)
 	return "Width and height must both be positive";
+    if (params->w > INT_MAX / params->h)
+        return "Width times height must not be unreasonably large";
 
     if (params->ncols > 9)
 	return "Maximum of 9 colours";