diff --git a/ANNOUNCE b/ANNOUNCE
index 1c5d31254..1f3edd760 100644
--- a/ANNOUNCE
+++ b/ANNOUNCE
@@ -26,6 +26,7 @@ Other information:
 Changes since the last public release (1.6.22):
 
 Version 1.6.23beta01 [May 28, 2016]
+  Stop a potential memory leak in png_set_tRNS() (Bug report by Ted Ying).
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
diff --git a/CHANGES b/CHANGES
index ba1ab5161..d31a5b398 100644
--- a/CHANGES
+++ b/CHANGES
@@ -5574,6 +5574,7 @@ Version 1.6.22 [May 26, 2016]
   No changes.
 
 Version 1.6.23beta01 [May 28, 2016]
+  Stop a potential memory leak in png_set_tRNS() (Bug report by Ted Ying).
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
diff --git a/pngset.c b/pngset.c
index 4bd5ab3cb..6e9c50aab 100644
--- a/pngset.c
+++ b/pngset.c
@@ -1,8 +1,8 @@
 
 /* pngset.c - storage of image information into info struct
  *
- * Last changed in libpng 1.6.21 [January 15, 2016]
- * Copyright (c) 1998-2015 Glenn Randers-Pehrson
+ * Last changed in libpng 1.6.23 [(PENDING RELEASE)]
+ * Copyright (c) 1998-2016 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.)
  *
@@ -952,12 +952,13 @@ png_set_tRNS(png_structrp png_ptr, png_inforp info_ptr,
 
        png_free_data(png_ptr, info_ptr, PNG_FREE_TRNS, 0);
 
-       /* Changed from num_trans to PNG_MAX_PALETTE_LENGTH in version 1.2.1 */
-       png_ptr->trans_alpha = info_ptr->trans_alpha = png_voidcast(png_bytep,
-         png_malloc(png_ptr, PNG_MAX_PALETTE_LENGTH));
-
        if (num_trans > 0 && num_trans <= PNG_MAX_PALETTE_LENGTH)
+       {
+         /* Changed from num_trans to PNG_MAX_PALETTE_LENGTH in version 1.2.1 */
+          png_ptr->trans_alpha = info_ptr->trans_alpha = png_voidcast(png_bytep,
+             png_malloc(png_ptr, PNG_MAX_PALETTE_LENGTH));
           memcpy(info_ptr->trans_alpha, trans_alpha, (png_size_t)num_trans);
+       }
    }
 
    if (trans_color != NULL)