diff --git a/src/language/PEGGrammar.hpp b/src/language/PEGGrammar.hpp
index 245096229787e862b7b651926890e310aff902a5..bc2556cdc011eb169e7ba11b2f3b67ede9db87b4 100644
--- a/src/language/PEGGrammar.hpp
+++ b/src/language/PEGGrammar.hpp
@@ -60,10 +60,10 @@ struct LITERAL : seq< literal, ignored >{};
 
 struct REAL : seq< real, ignored >{};
 
-struct B_set : one< 'B' >{};
-struct N_set : one< 'N' >{};
-struct Z_set : one< 'Z' >{};
-struct R_set : one< 'R' >{};
+struct B_set : TAO_PEGTL_KEYWORD("B"){};
+struct N_set : TAO_PEGTL_KEYWORD("N"){};
+struct Z_set : TAO_PEGTL_KEYWORD("Z"){};
+struct R_set : TAO_PEGTL_KEYWORD("R"){};
 
 struct string_type : TAO_PEGTL_KEYWORD("string") {};