diff --git a/util/lintlib.py b/util/lintlib.py
index c386a94b18b..1c49ab770d5 100644
--- a/util/lintlib.py
+++ b/util/lintlib.py
@@ -72,10 +72,13 @@ def parse_lints(lints, filepath):
                             g = group_re.search(line)
                             if g:
                                 group = g.group(1).lower()
-                                level = lint_levels[group]
+                                level = lint_levels.get(group, None)
                                 break
                             line = next(fp)
 
+                    if level is None:
+                        continue
+
                     log.info("found %s with level %s in %s",
                              name, level, filepath)
                     lints.append(Lint(name, level, last_comment, filepath, group))
@@ -103,9 +106,11 @@ def parse_configs(path):
 
 def parse_all(path="clippy_lints/src"):
     lints = []
-    for filename in os.listdir(path):
-        if filename.endswith(".rs"):
-            parse_lints(lints, os.path.join(path, filename))
+    for root, dirs, files in os.walk(path):
+        for fn in files:
+            if fn.endswith('.rs'):
+                parse_lints(lints, os.path.join(root, fn))
+
     log.info("got %s lints", len(lints))
 
     configs = parse_configs(path)