libpng: Version 1.5.1beta04 [January 16, 2011]
  Mentioned in the documentation that applications must #include "zlib.h"
    if they need access to anything in zlib.h.
---
 codec/convert.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/codec/convert.c b/codec/convert.c
index 25e715b..153c4b9 100644
--- a/codec/convert.c
+++ b/codec/convert.c
@@ -47,6 +47,7 @@
 #ifdef _WIN32
 #include "../libs/png/png.h"
 #else
+#include <zlib.h>
 #include <png.h>
 #endif /* _WIN32 */
 #endif /* HAVE_LIBPNG */