--- ufoai-2.3.1-source/src/shared/images.c	
+++ ufoai-2.3.1-source/src/shared/images.c	
@@ -32,6 +32,7 @@ 
 
 #include <jpeglib.h>
 #include <png.h>
+#include <zlib.h>
 
 /** image formats, tried in this order */
 static char *IMAGE_TYPES[] = { "tga", "png", "jpg", NULL };