1 files changed, 6 insertions, 1 deletions
diff --git a/bignum.c b/bignum.c
index 6882580eae..7c3e029d57 100644
--- a/bignum.c
+++ b/bignum.c
@@ -729,7 +729,12 @@ rb_big2ulong(x)
 {
     unsigned long num = big2ulong(x, "unsigned long");
 
-    if (!RBIGNUM(x)->sign) return -num;
+    if (!RBIGNUM(x)->sign) {
+	if ((long)num < 0) {
+	    rb_raise(rb_eRangeError, "bignum out of range of unsigned long");
+	}
+	return -num;
+    }
     return num;
 }