diff --git a/untangle.c b/untangle.c
index 06ed90c..1453afb 100644
--- a/untangle.c
+++ b/untangle.c
@@ -31,6 +31,7 @@
 #include <string.h>
 #include <assert.h>
 #include <ctype.h>
+#include <limits.h>
 #include <math.h>
 
 #include "puzzles.h"
@@ -206,6 +207,8 @@ static const char *validate_params(const game_params *params, bool full)
 {
     if (params->n < 4)
         return "Number of points must be at least four";
+    if (params->n > INT_MAX / 3)
+        return "Number of points must not be unreasonably large";
     return NULL;
 }