diff --git a/src/core/RpUnits.h b/src/core/RpUnits.h
index e697424..fb9b3b5 100644
--- a/src/core/RpUnits.h
+++ b/src/core/RpUnits.h
@@ -393,9 +393,7 @@ class RpUnits
             return true;
 
         }
-        struct _key_compare:
-            public
-            std::binary_function<std::string,std::string,bool> {
+        struct _key_compare {
 
                 bool operator() (   const std::string& lhs,
                                     const std::string& rhs ) const