diff --git a/pnglibconf.h b/pnglibconf.h
index f5971c8..21772fe 100644
--- a/pnglibconf.h
+++ b/pnglibconf.h
@@ -40,6 +40,7 @@
 #define PNG_GET_PALETTE_MAX_SUPPORTED
 #define PNG_HANDLE_AS_UNKNOWN_SUPPORTED
 #define PNG_INCH_CONVERSIONS_SUPPORTED
+#define PNG_INDEX_SUPPORTED
 #define PNG_INFO_IMAGE_SUPPORTED
 #define PNG_IO_STATE_SUPPORTED
 #define PNG_MNG_FEATURES_SUPPORTED