diff --git a/time/tzfile.c b/time/tzfile.c
index 190a777152..8668392ad3 100644
--- a/time/tzfile.c
+++ b/time/tzfile.c
@@ -431,8 +431,8 @@ __tzfile_read (const char *file, size_t extra, char **extrap)
   if (__tzname[0] == NULL)
     {
       /* This should only happen if there are no transition rules.
-	 In this case there should be only one single type.  */
-      assert (num_types == 1);
+	 In this case there's usually only one single type, unless
+	 e.g. the data file has a truncated time-range.  */
       __tzname[0] = __tzstring (zone_names);
     }
   if (__tzname[1] == NULL)