diff --git a/src/symbolizer_keys.cpp b/src/symbolizer_keys.cpp
index a2d343edb..f6615c3e9 100644
--- a/src/symbolizer_keys.cpp
+++ b/src/symbolizer_keys.cpp
@@ -29,8 +29,10 @@
 
 namespace mapnik {
 
+static constexpr std::uint8_t const_max_key = static_cast<std::uint8_t>(keys::MAX_SYMBOLIZER_KEY);
+
 // tuple -> name, default value, enumeration to string converter lambda, target property type
-static const property_meta_type key_meta[to_integral(keys::MAX_SYMBOLIZER_KEY)] =
+static const property_meta_type key_meta[const_max_key] =
 {
     property_meta_type{ "gamma", 1.0, nullptr, property_types::target_double},
     property_meta_type{ "gamma-method", static_cast<value_integer>(GAMMA_POWER), nullptr, property_types::target_gamma_method},
@@ -127,7 +129,7 @@ mapnik::keys get_key(std::string const& name)
 {
     std::string name_copy(name);
     boost::algorithm::replace_all(name_copy,"_","-");
-    for (unsigned i=0; i< to_integral(keys::MAX_SYMBOLIZER_KEY) ; ++i)
+    for (unsigned i=0; i< const_max_key ; ++i)
     {
         property_meta_type const& item = key_meta[i];
         if (name_copy == std::get<0>(item))
@@ -139,4 +141,4 @@ mapnik::keys get_key(std::string const& name)
     return static_cast<mapnik::keys>(0);
 }
 
-}
+}
\ No newline at end of file