diff --git a/include/mapnik/unicode.hpp b/include/mapnik/unicode.hpp
index ae2139a5e..0de34ac98 100644
--- a/include/mapnik/unicode.hpp
+++ b/include/mapnik/unicode.hpp
@@ -51,4 +51,10 @@ private:
 };
 }
 
+namespace icu_50 {
+inline std::size_t hash_value(const UnicodeString& val) {
+    return val.hashCode();
+}
+}
+
 #endif // MAPNIK_UNICODE_HPP
diff --git a/include/mapnik/value.hpp b/include/mapnik/value.hpp
index 41f51a087..40f329f33 100644
--- a/include/mapnik/value.hpp
+++ b/include/mapnik/value.hpp
@@ -36,6 +36,7 @@
 #include <boost/variant/variant.hpp>
 #include <boost/scoped_array.hpp>
 #include <boost/concept_check.hpp>
+#include <boost/functional/hash.hpp>
 
 // stl
 #include <iostream>
@@ -905,6 +906,10 @@ operator << (std::basic_ostream<charT,traits>& out,
     return out;
 }
 
+inline std::size_t hash_value(const value& val) {
+    return hash_value(val.base());
+}
+
 } // namespace value_adl_barrier
 
 using value_adl_barrier::value;
diff --git a/include/mapnik/value_types.hpp b/include/mapnik/value_types.hpp
index 7a73a8721..d80bd19cd 100644
--- a/include/mapnik/value_types.hpp
+++ b/include/mapnik/value_types.hpp
@@ -78,6 +78,10 @@ struct value_null
     }
 };
 
+inline std::size_t hash_value(const value_null& val) {
+    return 0;
+}
+
 inline std::ostream& operator<< (std::ostream & out,value_null const& v)
 {
     return out;