diff --git a/benchmark/test_to_bool.cpp b/benchmark/test_to_bool.cpp
new file mode 100644
index 000000000..92f073156
--- /dev/null
+++ b/benchmark/test_to_bool.cpp
@@ -0,0 +1,29 @@
+#include "bench_framework.hpp"
+#include <mapnik/util/conversions.hpp>
+
+class test : public benchmark::test_case
+{
+    std::string value_;
+public:
+    test(mapnik::parameters const& params)
+     : test_case(params),
+       value_("true") {}
+    bool validate() const
+    {
+        bool result = false;
+        mapnik::util::string2bool(value_.data(),value_.data()+value_.size(),result);
+        if (!result) return result;
+        mapnik::util::string2bool(value_,result);
+        return (result == true);
+    }
+    void operator()() const
+    {
+        for (std::size_t i=0;i<iterations_;++i) {
+            bool result = false;
+            mapnik::util::string2bool(value_,result);
+            mapnik::util::string2bool(value_.data(),value_.data()+value_.size(),result);
+        }
+    }
+};
+
+BENCHMARK(test,"string->bool")
diff --git a/include/mapnik/util/conversions.hpp b/include/mapnik/util/conversions.hpp
index 9c7c0a514..33d5301ea 100644
--- a/include/mapnik/util/conversions.hpp
+++ b/include/mapnik/util/conversions.hpp
@@ -38,8 +38,26 @@ to avoid the compile time overhead given it is included
 by many other headers inside mapnik.
 */
 
-MAPNIK_DECL bool string2bool(std::string const& value, bool & result);
-MAPNIK_DECL bool string2bool(const char * iter, const char * end, bool & result);
+MAPNIK_DECL inline bool string2bool(std::string const& value, bool & result)
+{
+    if (value == "true") {
+        return result = true;
+    } else if (value == "false") {
+        return result = false;
+    }
+    std::string val(value);
+    std::transform(val.begin(), val.end(), val.begin(), ::tolower);
+    if (val == "true" || val == "yes" || val == "1" || val == "on") {
+        return result = true;
+    }
+    return result = false;
+}
+
+MAPNIK_DECL inline bool string2bool(const char * iter, const char * end, bool & result)
+{
+    std::string val(iter,end);
+    return string2bool(val,result);
+}
 
 MAPNIK_DECL bool string2int(std::string const& value, int & result);
 MAPNIK_DECL bool string2int(const char * iter, const char * end, int & result);
diff --git a/src/conversions.cpp b/src/conversions.cpp
index 2b5a496b4..915242f9d 100644
--- a/src/conversions.cpp
+++ b/src/conversions.cpp
@@ -25,6 +25,7 @@
 #include <mapnik/value_types.hpp>
 
 #include <cstring>
+#include <algorithm>
 
 #include <boost/spirit/include/qi.hpp>
 
@@ -59,39 +60,6 @@ BOOST_SPIRIT_AUTO(qi, LONGLONG, qi::long_long_type())
 BOOST_SPIRIT_AUTO(qi, FLOAT, qi::float_type())
 BOOST_SPIRIT_AUTO(qi, DOUBLE, qi::double_type())
 
-struct bool_symbols : qi::symbols<char,bool>
-{
-    bool_symbols()
-    {
-        add("true",true)
-            ("false",false)
-            ("yes",true)
-            ("no",false)
-            ("on",true)
-            ("off",false)
-            ("1",true)
-            ("0",false);
-    }
-};
-
-bool string2bool(const char * iter, const char * end, bool & result)
-{
-    boost::spirit::qi::no_case_type no_case;
-    ascii::space_type space;
-    bool r = qi::phrase_parse(iter,end,no_case[bool_symbols()],space,result);
-    return r && (iter == end);
-}
-
-bool string2bool(std::string const& value, bool & result)
-{
-    boost::spirit::qi::no_case_type no_case;
-    ascii::space_type space;
-    std::string::const_iterator str_beg = value.begin();
-    std::string::const_iterator str_end = value.end();
-    bool r = qi::phrase_parse(str_beg,str_end,no_case[bool_symbols()],space,result);
-    return r && (str_beg == str_end);
-}
-
 bool string2int(const char * iter, const char * end, int & result)
 {
     ascii::space_type space;