1 files changed, 19 insertions, 1 deletions
diff --git a/lib/spack/llnl/util/lang.py b/lib/spack/llnl/util/lang.py
index 4943c9df67..9821ec7416 100644
--- a/lib/spack/llnl/util/lang.py
+++ b/lib/spack/llnl/util/lang.py
@@ -266,10 +266,28 @@ def key_ordering(cls):
 
 
 @key_ordering
-class HashableMap(dict):
+class HashableMap(collections.MutableMapping):
     """This is a hashable, comparable dictionary.  Hash is performed on
        a tuple of the values in the dictionary."""
 
+    def __init__(self):
+        self.dict = {}
+
+    def __getitem__(self, key):
+        return self.dict[key]
+
+    def __setitem__(self, key, value):
+        self.dict[key] = value
+
+    def __iter__(self):
+        return iter(self.dict)
+
+    def __len__(self):
+        return len(self.dict)
+
+    def __delitem__(self, key):
+        del self.dict[key]
+
     def _cmp_key(self):
         return tuple(sorted(self.values()))