diff --git a/src/OpenFOAM/containers/HashTables/HashSet/HashSet.H b/src/OpenFOAM/containers/HashTables/HashSet/HashSet.H
index 654b743add..3985e574fb 100644
--- a/src/OpenFOAM/containers/HashTables/HashSet/HashSet.H
+++ b/src/OpenFOAM/containers/HashTables/HashSet/HashSet.H
@@ -100,6 +100,17 @@ public:
             {
                 return HashTable<empty, Key, Hash>::insert(key, empty());
             }
+
+
+    // Member Operators
+
+        //- Equality. Two hashtables are equal if all contents of first are
+        //  also in second and vice versa. So does not depend on table size or
+        //  order!
+        bool operator==(const HashSet<Key, Hash>&) const;
+
+        //- The opposite of the equality operation.
+        bool operator!=(const HashSet<Key, Hash>&) const;
 };
 
 
@@ -112,6 +123,12 @@ typedef HashSet<> wordHashSet;
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
+#ifdef NoRepository
+#   include "HashSet.C"
+#endif
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
 #endif
 
 // ************************************************************************* //