1 files changed, 4 insertions, 0 deletions
diff --git a/pkg_resources.py b/pkg_resources.py
index e8dae8a4..4cc73bb8 100644
--- a/pkg_resources.py
+++ b/pkg_resources.py
@@ -508,6 +508,10 @@ class WorkingSet(object):
         """
         seen = {}
         for item in self.entries:
+            if item not in self.entry_keys:
+                # workaround a cache issue
+                continue
+
             for key in self.entry_keys[item]:
                 if key not in seen:
                     seen[key]=1