diff --git a/vanir/language_parsers/language_parsers.py b/vanir/language_parsers/language_parsers.py
index f2d5b8b..5578004 100644
--- a/vanir/language_parsers/language_parsers.py
+++ b/vanir/language_parsers/language_parsers.py
@@ -28,9 +28,19 @@
 _P = TypeVar('_P', bound=abstract_language_parser.AbstractLanguageParser)
 
 
+def _all_subclasses(cls):
+  """Recursively collect all concrete (non-abstract) subclasses of cls."""
+  result = []
+  for sub in cls.__subclasses__():
+    if not sub.__abstractmethods__:
+      result.append(sub)
+    result.extend(_all_subclasses(sub))
+  return result
+
+
 def get_parser_class(filename: str) -> Optional[Type[_P]]:
   """Returns the language parser class that handles the given file, or None."""
-  parsers = abstract_language_parser.AbstractLanguageParser.__subclasses__()
+  parsers = _all_subclasses(abstract_language_parser.AbstractLanguageParser)
   ext = os.path.splitext(filename)[1]
   for parser_class in parsers:
     if ext in parser_class.get_supported_extensions():