diff --git a/agenda/thespacedevs.py b/agenda/thespacedevs.py
index 36993e9..8ca9428 100644
--- a/agenda/thespacedevs.py
+++ b/agenda/thespacedevs.py
@@ -156,7 +156,9 @@ def get_launches(
 ) -> list[Summary]:
     """Get rocket launches with caching."""
     now = datetime.now()
-    existing = [x for x in (filename_timestamp(f) for f in os.listdir(rocket_dir)) if x]
+    existing = [
+        x for x in (filename_timestamp(f, "json") for f in os.listdir(rocket_dir)) if x
+    ]
 
     existing.sort(reverse=True)