diff --git a/include/mapnik/expression_grammar_impl.hpp b/include/mapnik/expression_grammar_impl.hpp
index 8c66cf351..b760d5232 100644
--- a/include/mapnik/expression_grammar_impl.hpp
+++ b/include/mapnik/expression_grammar_impl.hpp
@@ -185,13 +185,13 @@ expression_grammar<Iterator>::expression_grammar(mapnik::transcoder const& tr)
         >> *(unesc_char | "\\x" >> hex | (char_ - lit(_a)))
         >> lit(_a);
     attr %= '[' >> no_skip[+~char_(']')] >> ']';
-    global_attr %= '@' >> no_skip[alpha >> *alnum];
+    global_attr %= '@' >> no_skip[alpha >> * (alnum | char_('-'))];
 #else
     quoted_ustring %= lit('\'')
         >> *(unesc_char | "\\x" >> hex | (char_ - lit('\'')))
         >> lit('\'');
     attr %= '[' >> lexeme[+(char_ - ']')] >> ']';
-    global_attr %= '@' >> no_skip[alpha >> *alnum];
+    global_attr %= '@' >> no_skip[alpha >> * (alnum | char_('-'))];
 #endif
 
 }