diff --git a/tools/build-gtk-stack b/tools/build-gtk-stack
index 96e3f4bc3e..434ad95b94 100755
--- a/tools/build-gtk-stack
+++ b/tools/build-gtk-stack
@@ -148,7 +148,7 @@ defmod 'expat' '2.1.0' 'http://prdownloads.sourceforge.net/expat/' 'gz'
 defmod 'libxml2' '2.7.8' 'ftp://xmlsoft.org/libxslt/' 'gz'
 defmod 'libxslt' '1.1.28' 'ftp://xmlsoft.org/libxslt/' 'gz'
 defmod 'tiff' '4.0.1' 'ftp://ftp.remotesensing.org/pub/libtiff/' 'gz'
-defmod 'libpng' '1.6.0' 'ftp://ftp.simplesystems.org/pub/libpng/png/src/libpng16' 'xz'
+defmod 'libpng' '1.6.0' 'ftp://ftp.simplesystems.org/pub/libpng/png/src/libpng16/' 'xz'
 defmod 'jpeg' 'jpegsrc.v8d' '' 'http://www.ijg.org/files/' 'gz' 'jpeg-8d'
 defmod 'makemaker' 'ExtUtils-MakeMaker' '6.64' 'http://search.cpan.org/CPAN/authors/id/M/MS/MSCHWERN/' 'gz'
 defmod 'xmlparser' 'XML-Parser' '2.41' 'http://search.cpan.org/CPAN/authors/id/T/TO/TODDR/' 'gz'