diff --git a/include/mapnik/css_color_grammar_def.hpp b/include/mapnik/css_color_grammar_impl.hpp
similarity index 95%
rename from include/mapnik/css_color_grammar_def.hpp
rename to include/mapnik/css_color_grammar_impl.hpp
index 028411ba1..5b37f8761 100644
--- a/include/mapnik/css_color_grammar_def.hpp
+++ b/include/mapnik/css_color_grammar_impl.hpp
@@ -20,8 +20,8 @@
  *
  *****************************************************************************/
 
-#ifndef MAPNIK_CSS_COLOR_GRAMMAR_DEF_HPP
-#define MAPNIK_CSS_COLOR_GRAMMAR_DEF_HPP
+// NOTE: This is an implementation header file and is only meant to be included
+//    from implementation files. It therefore doesn't have an include guard.
 
 // boost
 #include <boost/version.hpp>
@@ -100,5 +100,3 @@ css_color_grammar<Iterator>::css_color_grammar()
 }
 
 #endif
-
-#endif
diff --git a/src/css_color_grammar.cpp b/src/css_color_grammar.cpp
index 6a8be6d1d..df36b5d44 100644
--- a/src/css_color_grammar.cpp
+++ b/src/css_color_grammar.cpp
@@ -25,7 +25,7 @@
 
 #if BOOST_VERSION >= 104500
 
-#include <mapnik/css_color_grammar_def.hpp>
+#include <mapnik/css_color_grammar_impl.hpp>
 
 namespace mapnik
 {