diff --git a/cronwrapper/__init__.py b/cronwrapper/__init__.py
index 28df779..254d1a0 100755
--- a/cronwrapper/__init__.py
+++ b/cronwrapper/__init__.py
@@ -217,7 +217,9 @@ def main():
     if previous_runs:
         # Not the first failure...
         oldest = datetime.datetime.fromtimestamp(min(previous_runs.values()))
-        if now-oldest > datetime.timedelta(seconds=args.warn_interval):
+        delta = datetime.timedelta(seconds=args.warn_interval)
+        diff = now-oldest
+        if diff > delta:
             # we have failed for a long time, send a report
             print("Cronjob is still failing after {} seconds ({} failures)\n".format(args.warn_interval, len(previous_runs)))
             print_runs(previous_runs.keys())