diff --git a/.travis.yml b/.travis.yml
index b40a16d8fb..f6c83997aa 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -13,7 +13,8 @@ before_script:
   - sudo apt-get update -qq
   - sudo apt-get install -qq python-yaml
   - git remote add upstream git://github.com/dotcloud/docker.git
-  - git fetch upstream +refs/heads/master:refs/remotes/upstream/master
+  - git fetch --append --no-tags upstream refs/heads/master:refs/remotes/upstream/master
+# sometimes we have upstream master already as origin/master (PRs), but other times we don't, so let's just make sure we have a completely unambiguous way to specify "upstream master" from here out
 
 script:
   - hack/travis/dco.py
diff --git a/hack/travis/dco.py b/hack/travis/dco.py
index bca84bfe75..6a875863a1 100755
--- a/hack/travis/dco.py
+++ b/hack/travis/dco.py
@@ -24,6 +24,14 @@ p = re.compile(r'^{0} ([^<]+) <([^<>@]+@[^<>]+)> \(github: (\S+)\)$'.format(re.e
 failed_commits = 0
 
 for commit in commits:
+	commit['stat'] = subprocess.check_output([
+		'git', 'log', '--format=format:', '--max-count=1',
+		'--name-status', commit['hash'], '--',
+	])
+	if commit['stat'] == '':
+		print 'Commit {0} has no actual changed content, skipping.'.format(commit['hash'])
+		continue
+	
 	m = p.search(commit['message'])
 	if not m:
 		print 'Commit {1} does not have a properly formatted "{0}" marker.'.format(DCO, commit['hash'])