diff --git a/lib/dns/tsig.c b/lib/dns/tsig.c
index fe881f59da..38879efee4 100644
--- a/lib/dns/tsig.c
+++ b/lib/dns/tsig.c
@@ -16,7 +16,7 @@
  */
 
 /*
- * $Id: tsig.c,v 1.149 2011/08/25 06:20:07 marka Exp $
+ * $Id: tsig.c,v 1.150 2011/08/29 04:02:54 marka Exp $
  */
 /*! \file */
 #include <config.h>
@@ -1018,8 +1018,10 @@ dns_tsig_sign(dns_message_t *msg) {
 		}
 		/* Digest the timesigned and fudge */
 		isc_buffer_clear(&databuf);
-		if (tsig.error == dns_tsigerror_badtime)
+		if (tsig.error == dns_tsigerror_badtime) {
+			INSIST(response);
 			tsig.timesigned = querytsig.timesigned;
+		}
 		isc_buffer_putuint48(&databuf, tsig.timesigned);
 		isc_buffer_putuint16(&databuf, tsig.fudge);
 		isc_buffer_usedregion(&databuf, &r);