diff --git a/lib/spack/spack/repo.py b/lib/spack/spack/repo.py
index 11a4e144160..814f84049a3 100644
--- a/lib/spack/spack/repo.py
+++ b/lib/spack/spack/repo.py
@@ -1478,6 +1478,8 @@ def __init__(self, name, repo=None):
             if name.endswith(".yaml"):
                 long_msg = "Did you mean to specify a filename with './{0}'?"
                 long_msg = long_msg.format(name)
+            else:
+                long_msg = "You may need to run 'spack clean -m'."
         else:
             msg = "Attempting to retrieve anonymous package."