diff --git a/turtle/constraint.hpp b/turtle/constraint.hpp
index 34817ac..3c62576 100644
--- a/turtle/constraint.hpp
+++ b/turtle/constraint.hpp
@@ -153,6 +153,11 @@ namespace detail
             {} \
             template< typename Actual > \
             bool operator()( const Actual& actual ) const \
+            { \
+                return test( actual, boost::unwrap_ref( expected_ ) ); \
+            } \
+            template< typename Actual, typename T > \
+            bool test( const Actual& actual, const T& expected ) const \
             { \
                 return Expr; \
             } \
diff --git a/turtle/constraints.hpp b/turtle/constraints.hpp
index a13ebbe..6feafed 100644
--- a/turtle/constraints.hpp
+++ b/turtle/constraints.hpp
@@ -23,13 +23,11 @@ namespace mock
     MOCK_UNARY_CONSTRAINT( negate, ! actual )
     MOCK_UNARY_CONSTRAINT( evaluate, actual() )
 
-    MOCK_BINARY_CONSTRAINT( equal, actual == boost::unwrap_ref( expected_ ) )
-    MOCK_BINARY_CONSTRAINT( less, actual < boost::unwrap_ref( expected_ ) )
-    MOCK_BINARY_CONSTRAINT( greater, actual > boost::unwrap_ref( expected_ ) )
-    MOCK_BINARY_CONSTRAINT(
-        less_equal, actual <= boost::unwrap_ref( expected_ ) )
-    MOCK_BINARY_CONSTRAINT(
-        greater_equal, actual >= boost::unwrap_ref( expected_ ) )
+    MOCK_BINARY_CONSTRAINT( equal, actual == expected )
+    MOCK_BINARY_CONSTRAINT( less, actual < expected )
+    MOCK_BINARY_CONSTRAINT( greater, actual > expected )
+    MOCK_BINARY_CONSTRAINT( less_equal, actual <= expected )
+    MOCK_BINARY_CONSTRAINT( greater_equal, actual >= expected )
 
 namespace detail
 {