diff --git a/src/script/build-integration-branch b/src/script/build-integration-branch
index 3e13ffb323f..416d38e8b86 100755
--- a/src/script/build-integration-branch
+++ b/src/script/build-integration-branch
@@ -42,17 +42,18 @@ print "branch %s" % branch
 
 # assemble
 print('--- creating branch %s' % branch)
-call(['git', 'branch', '-D', branch])
-call(['git', 'checkout', '-b', branch])
+r = call(['git', 'checkout', '-b', branch])
+assert not r
 for pr in prs:
     print('--- pr %d --- pulling %s branch %s' % (
         pr['number'],
         pr['head']['repo']['clone_url'],
         pr['head']['ref']))
-    call(['git', 'pull', '--no-edit',
+    r = call(['git', 'pull', '--no-edit',
           pr['head']['repo']['clone_url'],
           pr['head']['ref']
     ])
+    assert not r
 print('--- done. these PRs were included:')
 print('\n'.join(prtext))
 print('--- perhaps you want to: make && ctest -j12 && git push ci %s' % branch)