diff --git a/turtle/config.hpp b/turtle/config.hpp
index 673ca08..3646d90 100644
--- a/turtle/config.hpp
+++ b/turtle/config.hpp
@@ -31,6 +31,11 @@
 #endif
 
 #ifdef MOCK_USE_BOOST_PHOENIX
+#   ifndef BOOST_RESULT_OF_NUM_ARGS
+#       define BOOST_RESULT_OF_NUM_ARGS MOCK_MAX_ARGS
+#   elif BOOST_PP_LESS(BOOST_RESULT_OF_NUM_ARGS, MOCK_MAX_ARGS)
+#       error BOOST_RESULT_OF_NUM_ARGS must be set to MOCK_MAX_ARGS or higher
+#   endif
 #   ifndef PHOENIX_LIMIT
 #       define PHOENIX_LIMIT MOCK_MAX_ARGS
 #   elif BOOST_PP_LESS(PHOENIX_LIMIT, MOCK_MAX_ARGS)