diff --git a/tests/test_recur.py b/tests/test_recur.py
index b79b2fe..9c29d55 100644
--- a/tests/test_recur.py
+++ b/tests/test_recur.py
@@ -169,5 +169,9 @@ def test_annually():
 
 
 def test_unsupported():
-    pass
+    with pytest.raises(Exception):
+        utils.parse_recur('every mon,tues,weds')
+
+    with pytest.raises(Exception):
+        utils.parse_recur('every monday,tuesday,wednesday')
 
diff --git a/todoist_taskwarrior/utils.py b/todoist_taskwarrior/utils.py
index 7464a3e..059bc63 100644
--- a/todoist_taskwarrior/utils.py
+++ b/todoist_taskwarrior/utils.py
@@ -86,13 +86,16 @@ def parse_recur(date_string):
     # - trim leading, trailing, and, duplicate spaces
     # - convert to lowercase
     date_string = ' '.join(date_string.lower().strip().split())
-    return (
+    result = (
         _recur_single_cycle(date_string) or
         _recur_multi_cycle(date_string) or
         _recur_day_of_week(date_string) or
         _recur_day_of_month(date_string) or
         _recur_special(date_string)
     )
+    if not result:
+        raise Exception("Recurrence not supported: %s" % date_string)
+    return result
 
 
 # Atoms