diff --git a/scripts/pnglibconf.dfa b/scripts/pnglibconf.dfa
index ea40ccf07..4351dc322 100644
--- a/scripts/pnglibconf.dfa
+++ b/scripts/pnglibconf.dfa
@@ -223,6 +223,7 @@ setting USER_CHUNK_MALLOC_MAX default 0
 
 # READ options
 option READ enables READ_INTERLACING
+option READ_QUANTIZE requires READ
 
 option READ_TRANSFORMS requires READ
 = NO_READ_TRANSFORMS PNG_READ_TRANSFORMS_NOT_SUPPORTED
@@ -265,9 +266,6 @@ option INCH_CONVERSIONS requires FLOATING_POINT off
 # IN DEVELOPMENT
 # These are currently experimental features, define them if you want
 
-# Never enabled?
-option READ_DITHER requires READ off
-
 # Very little testing, not enabled by default.
 option READ_16_TO_8_ACCURATE_SCALE requires READ off
 
diff --git a/scripts/symbols.dfn b/scripts/symbols.dfn
index 534c19dcf..19dc64375 100644
--- a/scripts/symbols.dfn
+++ b/scripts/symbols.dfn
@@ -1,7 +1,7 @@
 
 /* symbols.dfn - find all exported symbols
  *
- * Last changed in libpng 1.5.0 [April 1, 2010]
+ * Last changed in libpng 1.5.0 [April 17, 2010]
  * Copyright (c) 1998-2010 Glenn Randers-Pehrson
  *
  * This code is released under the libpng license.
@@ -41,7 +41,7 @@
 #define PNG_ERROR_NUMBERS_SUPPORTED
 #define PNG_READ_BIG_ENDIAN_SUPPORTED  /* should do nothing! */
 #define PNG_INCH_CONVERSIONS_SUPPORTED
-#define PNG_READ_DITHER_SUPPORTED
+#define PNG_READ_QUANTIZE_SUPPORTED
 #define PNG_READ_16_TO_8_ACCURATE_SCALE_SUPPORTED
 
 #undef PNG_H