diff --git a/demo/viewer/mainwindow.cpp b/demo/viewer/mainwindow.cpp
index 436a31ddc..c4fc631b6 100644
--- a/demo/viewer/mainwindow.cpp
+++ b/demo/viewer/mainwindow.cpp
@@ -40,6 +40,7 @@
 #include <mapnik/config_error.hpp>
 #include <mapnik/load_map.hpp>
 #include <mapnik/save_map.hpp>
+#include <mapnik/projection.hpp>
 #endif
 
 // qt