diff --git a/tww/lib.py b/tww/lib.py
index e8ce18b..3591329 100644
--- a/tww/lib.py
+++ b/tww/lib.py
@@ -487,7 +487,10 @@ def tzinfo_from_offset(offset: str) -> pytz.timezone:
 
 
 def custom_dt_parse(query):
-    with open(os.path.join(basepath, "data", "custom_dt.csv")) as f:
+    custom_dt_file = os.path.join(basepath, "data", "custom_dt.csv")
+    if not os.path.exists(custom_dt_file):
+        return query
+    with open(custom_dt_file) as f:
         cfile = csv.reader(f)
         for row in cfile:
             entry = row[0]