diff --git a/ANNOUNCE b/ANNOUNCE
index 4317f36ed..0a57eff19 100644
--- a/ANNOUNCE
+++ b/ANNOUNCE
@@ -39,7 +39,11 @@ Version 1.6.20beta03 [November 25, 2015]
  
 Version 1.6.20rc01 [November 25, 2015]
   Fixed an error in handling of bad zlib CMINFO field, found by American
-    Fuzzy Lop.
+    Fuzzy Lop, reported by Brian Carpenter.  inflate() doesn't immediately
+    fault a bad CMINFO field; instead a 'too far back' error happens later
+    (at least some times).  pngfix failed to limit CMINFO to the allowed
+    values but then assumed that window_bits was in range, triggering an
+    assert. The bug is mostly harmless; the file can't be fixed.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
diff --git a/CHANGES b/CHANGES
index 6c67dab25..20f17292d 100644
--- a/CHANGES
+++ b/CHANGES
@@ -5428,7 +5428,11 @@ Version 1.6.20beta03 [November 24, 2015]
 
 Version 1.6.20rc01 [November 25, 2015]
   Fixed an error in handling of bad zlib CMINFO field, found by American
-    Fuzzy Lop.
+    Fuzzy Lop, reported by Brian Carpenter.  inflate() doesn't immediately
+    fault a bad CMINFO field; instead a 'too far back' error happens later
+    (at least some times).  pngfix failed to limit CMINFO to the allowed
+    values but then assumed that window_bits was in range, triggering an
+    assert. The bug is mostly harmless; the file can't be fixed.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
diff --git a/contrib/libtests/readpng.c b/contrib/libtests/readpng.c
index 9d2a5be73..3336d4e21 100644
--- a/contrib/libtests/readpng.c
+++ b/contrib/libtests/readpng.c
@@ -62,6 +62,7 @@ read_png(FILE *fp)
    {
       png_size_t rowbytes = png_get_rowbytes(png_ptr, info_ptr);
 
+      /* Failure to initialize these is harmless */
       row = malloc(rowbytes);
       display = malloc(rowbytes);
 
@@ -73,7 +74,7 @@ read_png(FILE *fp)
 #        ifdef PNG_READ_INTERLACING_SUPPORTED
             int passes = png_set_interlace_handling(png_ptr);
 #        else /* !READ_INTERLACING */
-            int passes = png_get_interlace_type(png_ptr, info_ptr) == 
+            int passes = png_get_interlace_type(png_ptr, info_ptr) ==
                PNG_INTERLACE_ADAM7 ? PNG_INTERLACE_ADAM7_PASSES : 1;
 #        endif /* !READ_INTERLACING */
          int pass;
diff --git a/contrib/tools/pngfix.c b/contrib/tools/pngfix.c
index 3cdf81a1a..5135fd391 100644
--- a/contrib/tools/pngfix.c
+++ b/contrib/tools/pngfix.c
@@ -2,7 +2,7 @@
  *
  * Copyright (c) 2014-2015 John Cunningham Bowler
  *
- * Last changed in libpng 1.6.18 [July 23, 2015]
+ * Last changed in libpng 1.6.20 [(PENDING RELEASE)]
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer