--- tools/gxps-png-writer.c.zlib	2011-11-23 03:25:04.000000000 +0100
+++ tools/gxps-png-writer.c	2011-11-23 03:25:18.000000000 +0100
@@ -21,6 +21,7 @@
 
 #include "gxps-png-writer.h"
 #include <png.h>
+#include <zlib.h>
 #include <stdint.h>
 
 struct _GXPSPngWriter {