diff --git a/include/mapnik/well_known_srs.hpp b/include/mapnik/well_known_srs.hpp
index c7a6fe008..5efab629b 100644
--- a/include/mapnik/well_known_srs.hpp
+++ b/include/mapnik/well_known_srs.hpp
@@ -24,6 +24,7 @@
 #define MAPNIK_WELL_KNOWN_SRS_HPP
 
 // mapnik
+#include <mapnik/global.hpp> // for M_PI on windows
 #include <mapnik/enumeration.hpp>
 
 // boost