--- a/src/imageio/format/png.c 2011-09-21 20:22:51.354705840 +0200
+++ b/src/imageio/format/png.c 2011-09-21 20:22:40.305843971 +0200
@@ -27,6 +27,7 @@
 #include <stdlib.h>
 #include <stdio.h>
 #include <png.h>
+#include <zlib.h>
 #include <inttypes.h>
 
 DT_MODULE(1)