diff --git a/lib/spack/spack/cmd/extensions.py b/lib/spack/spack/cmd/extensions.py
index e1f30f7cf3c..bda20b9e1c8 100644
--- a/lib/spack/spack/cmd/extensions.py
+++ b/lib/spack/spack/cmd/extensions.py
@@ -90,7 +90,7 @@ def extensions(parser, args):
     # List specs of installed extensions.
     #
     installed = [s.spec
-                 for s in spack.store.db.activated_extensions_for(spec)]
+                 for s in spack.store.db.installed_extensions_for(spec)]
 
     print
     if not installed:
diff --git a/lib/spack/spack/database.py b/lib/spack/spack/database.py
index f8334dfa00b..90250c11ee9 100644
--- a/lib/spack/spack/database.py
+++ b/lib/spack/spack/database.py
@@ -740,6 +740,16 @@ def installed_relatives(self, spec, direction='children', transitive=True):
                 relatives.add(relative)
         return relatives
 
+    @_autospec
+    def installed_extensions_for(self, extendee_spec):
+        """
+        Return the specs of all packages that extend
+        the given spec
+        """
+        for spec in self.query():
+            if spec.package.extends(extendee_spec):
+                yield spec.package
+
     @_autospec
     def activated_extensions_for(self, extendee_spec):
         """