diff --git a/stevedore/_cache.py b/stevedore/_cache.py
index 20b631d..a7a83cc 100644
--- a/stevedore/_cache.py
+++ b/stevedore/_cache.py
@@ -56,7 +56,7 @@ def _get_mtime(name):
         s = os.stat(name)
         return s.st_mtime
     except OSError as err:
-        if err.errno != errno.ENOENT:
+        if err.errno not in {errno.ENOENT, errno.ENOTDIR}:
             raise
     return -1.0