diff --git a/pngrutil.c b/pngrutil.c
index 0a8baf877..841eb3d56 100644
--- a/pngrutil.c
+++ b/pngrutil.c
@@ -1,7 +1,7 @@
 
 /* pngrutil.c - utilities to read a PNG file
  *
- * Last changed in libpng 1.4.10 [February 20, 2012]
+ * Last changed in libpng 1.4.10 [February 21, 2012]
  * Copyright (c) 1998-2012 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
@@ -1581,15 +1581,16 @@ png_handle_hIST(png_structp png_ptr, png_infop info_ptr, png_uint_32 length)
       return;
    }
 
-   num = length / 2 ;
-   if (num != (unsigned int) png_ptr->num_palette || num >
-      (unsigned int) PNG_MAX_PALETTE_LENGTH)
+   if (length > 2*PNG_MAX_PALETTE_LENGTH ||
+       length != (unsigned int) (2*png_ptr->num_palette))
    {
       png_warning(png_ptr, "Incorrect hIST chunk length");
       png_crc_finish(png_ptr, length);
       return;
    }
 
+   num = length / 2 ;
+
    for (i = 0; i < num; i++)
    {
       png_byte buf[2];