diff --git a/lib/isc/unix/time.c b/lib/isc/unix/time.c
index c987d383dc..dbdb4f1089 100644
--- a/lib/isc/unix/time.c
+++ b/lib/isc/unix/time.c
@@ -15,7 +15,7 @@
  * WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
 
-/* $Id: time.c,v 1.39 2001/09/05 17:03:42 gson Exp $ */
+/* $Id: time.c,v 1.40 2001/09/05 17:05:47 gson Exp $ */
 
 #include <config.h>
 
@@ -399,8 +399,11 @@ isc_time_formattimestamp(const isc_time_t *t, char *buf, unsigned int len) {
 	REQUIRE(len > 0);
 
 	now = (time_t) t->seconds;
-	strftime(buf, len, "%b %d %X", localtime(&now));
-	flen = strlen(buf);
-	snprintf(buf + flen, len - flen,
-		 ".%03u", t->nanoseconds / 1000000);
+	flen = strftime(buf, len, "%b %d %X", localtime(&now));
+	INSIST(flen < len);
+	if (flen != 0)
+		snprintf(buf + flen, len - flen,
+			 ".%03u", t->nanoseconds / 1000000);
+	else
+                snprintf(buf, len, "Bad 00 99:99:99.999");
 }