diff --git a/src/misc.c b/src/misc.c
index 951449e..49738a2 100644
--- a/src/misc.c
+++ b/src/misc.c
@@ -257,6 +257,10 @@ code_timespec (struct timespec t, char sbuf[TIMESPEC_STRSIZE_BOUND])
   char *np;
   bool negative = s < 0;
 
+  /* ignore invalid values of ns */
+  if (BILLION <= ns || ns < 0)
+    ns = 0;
+
   if (negative && ns != 0)
     {
       s++;