diff --git a/pkgs/development/libraries/libpng/default.nix b/pkgs/development/libraries/libpng/default.nix
index 16fe511f1f1a..7ba9bfb54b37 100644
--- a/pkgs/development/libraries/libpng/default.nix
+++ b/pkgs/development/libraries/libpng/default.nix
@@ -2,6 +2,7 @@
 
 assert zlib != null;
 
+# If you want to upgrade libpng, look at libpng15 branch
 stdenv.mkDerivation rec {
   name = "libpng-1.2.46";