diff --git a/test/tc_definitions.rb b/test/tc_definitions.rb
index 675867e..757a134 100644
--- a/test/tc_definitions.rb
+++ b/test/tc_definitions.rb
@@ -178,7 +178,7 @@ def check_zdump_line(zone, line, max_year)
         end
       end
     else
-      assert_match(/\s=\sNULL\z/, line, "Unexpected zdump format")
+      assert_match(/(?:-?\d+\s\(gmtime failed\)\s=\s|\s=\s(?:NULL|-?\d+\s\(localtime failed\))\z)/, line, 'Unexpected zdump format')
     end
   end