diff --git a/ext/libpng17/pnglibconf.h b/ext/libpng17/pnglibconf.h
index f75c7c3a35..090f96398c 100644
--- a/ext/libpng17/pnglibconf.h
+++ b/ext/libpng17/pnglibconf.h
@@ -39,9 +39,9 @@
 #define PNG_INCH_CONVERSIONS_SUPPORTED
 #define PNG_INFO_IMAGE_SUPPORTED
 #define PNG_IO_STATE_SUPPORTED
-#define PNG_MNG_FEATURES_SUPPORTED
-#define PNG_MNG_READ_FEATURES_SUPPORTED
-#define PNG_MNG_WRITE_FEATURES_SUPPORTED
+// #define PNG_MNG_FEATURES_SUPPORTED
+// #define PNG_MNG_READ_FEATURES_SUPPORTED
+// #define PNG_MNG_WRITE_FEATURES_SUPPORTED
 #define PNG_PALETTE_MAX_SUPPORTED
 #define PNG_PROGRESSIVE_READ_SUPPORTED
 #define PNG_READ_16BIT_SUPPORTED
diff --git a/ext/libpng17/pngpriv.h b/ext/libpng17/pngpriv.h
index 15a3226d3d..8c5496ec18 100644
--- a/ext/libpng17/pngpriv.h
+++ b/ext/libpng17/pngpriv.h
@@ -347,7 +347,8 @@
 #  define debug_handled(cond) do {} while (0)
 #  if PNG_LIBPNG_BUILD_BASE_TYPE >= PNG_LIBPNG_BUILD_RC
      /* Make sure there are no 'UNTESTED' macros in released code: */
-#    define UNTESTED libpng untested code
+// #    define UNTESTED libpng untested code
+# define UNTESTED
 #  endif
 #  define NOT_REACHED do {} while (0)
 #else