I discovered a memleak in my application, so I wrote this little test, which passes on 0.24.x and fails on 0.26.0:

public static int main(string[] argv)
{
  Gst.init(ref argv);
  var pipe = new Gst.Pipeline("pipe");
  var bin = Gst.ElementFactory.make("fakesink", "somename");

  assert(bin.ref_count == 1);
  pipe.add(bin);
  pipe.remove(bin);
  assert(bin.ref_count == 1);

  stdout.printf("gstreamer: OK\n");
  return 0;
}

$ valac gstreamer.vala -g --pkg=gstreamer-1.0 --enable-experimental && ./gstreamer 
**
ERROR:/home/thedoc/projects/vms/test/gstreamer.vala:10:_vala_main: assertion failed: (bin.ref_count == 1)


$ pkg-config --modversion gstreamer-1.0 
1.4.3

$ valac --version
Vala 0.26.0



In the git-repo I found a series of commits to 0.24.x regarding this issue, but they got reverted in the current release:
https://git.gnome.org/browse/vala/commit/?h=0.24&id=8fd03272c3dea767f757f73d2ff2c8dde70c0331
https://git.gnome.org/browse/vala/commit/?h=0.24&id=8e25c2b52e4cfe286a988d9f86f5e5a86b7736cf
https://git.gnome.org/browse/vala/commit/?h=0.24&id=47868c96854fbdd146493b16ac8ab87f0f9cc8bd