diff --git a/tools/lib/logreader.py b/tools/lib/logreader.py
index 6c1174611b..d6c1cc90c2 100755
--- a/tools/lib/logreader.py
+++ b/tools/lib/logreader.py
@@ -161,12 +161,14 @@ def direct_source(file_or_url):
   return [file_or_url]
 
 def get_invalid_files(files):
-  return [f for f in files if f is None or not file_exists(f)]
+  for f in files:
+    if f is None or not file_exists(f):
+      yield f
 
 def check_source(source, *args):
   try:
     files = source(*args)
-    assert len(get_invalid_files(files)) == 0
+    assert next(get_invalid_files(files), None) is None
     return True, files
   except Exception:
     return False, None
@@ -177,7 +179,6 @@ def auto_source(*args):
     valid, ret = check_source(source, *args)
     if valid:
       return ret
-
   return comma_api_source(*args)
 
 def parse_useradmin(identifier):
@@ -256,7 +257,7 @@ class LogReader:
 
   def reset(self):
     self.logreader_identifiers = self._parse_identifiers(self.identifier)
-    invalid_count = len(get_invalid_files(self.logreader_identifiers))
+    invalid_count = len(list(get_invalid_files(self.logreader_identifiers)))
     assert invalid_count == 0, f"{invalid_count}/{len(self.logreader_identifiers)} invalid log(s) found, please ensure all logs \
 are uploaded or auto fallback to qlogs with '/a' selector at the end of the route name."