diff --git a/var/spack/repos/builtin/packages/atk/package.py b/var/spack/repos/builtin/packages/atk/package.py
index d5b6933ec3..0a7d48774d 100644
--- a/var/spack/repos/builtin/packages/atk/package.py
+++ b/var/spack/repos/builtin/packages/atk/package.py
@@ -42,7 +42,7 @@ class Atk(Package):
     def url_for_version(self, version):
         """Handle atk's version-based custom URLs."""
         url = 'http://ftp.gnome.org/pub/gnome/sources/atk'
-        return 'url+/%s/atk-%s.tar.xz' % (version.up_to(2), version)
+        return url + '/%s/atk-%s.tar.xz' % (version.up_to(2), version)
 
     def install(self, spec, prefix):
         configure("--prefix=%s" % prefix)