diff --git a/src/libraries/turtle/functional.hpp b/src/libraries/turtle/functional.hpp
index 3b0b2df..d319e93 100644
--- a/src/libraries/turtle/functional.hpp
+++ b/src/libraries/turtle/functional.hpp
@@ -138,7 +138,7 @@ namespace detail
         template< typename Y >
         bool operator()( const Y& y,
             BOOST_DEDUCED_TYPENAME boost::disable_if<
-                boost::is_convertible< Y*, T >, Y >::type* = 0 ) const
+                boost::is_convertible< const Y*, T >, Y >::type* = 0 ) const
         {
             t_.get() = y;
             return true;
diff --git a/src/tests/turtle_test/constraint_test.cpp b/src/tests/turtle_test/constraint_test.cpp
index e9a64af..f481e64 100644
--- a/src/tests/turtle_test/constraint_test.cpp
+++ b/src/tests/turtle_test/constraint_test.cpp
@@ -87,6 +87,12 @@ BOOST_AUTO_TEST_CASE( retrieve )
         BOOST_CHECK( mock::retrieve( i ).functor_( j ) );
         BOOST_CHECK_EQUAL( i, &j );
     }
+    {
+        const int* i = 0;
+        int j = 1;
+        BOOST_CHECK( mock::retrieve( i ).functor_( j ) );
+        BOOST_CHECK_EQUAL( i, &j );
+    }
     {
         int* i = 0;
         int j = 1;