diff --git a/functions.sh b/functions.sh
index 9fdaa7a3..fb94c63e 100644
--- a/functions.sh
+++ b/functions.sh
@@ -345,7 +345,12 @@ function setup_project {
     fi
 
     # Try the specified branch before the ZUUL_BRANCH.
-    OVERRIDE_ZUUL_REF=$(echo $ZUUL_REF | sed -e "s,$ZUUL_BRANCH,$branch,")
+    if [[ ! -z $ZUUL_BRANCH ]]; then
+        OVERRIDE_ZUUL_REF=$(echo $ZUUL_REF | sed -e "s,$ZUUL_BRANCH,$branch,")
+    else
+        OVERRIDE_ZUUL_REF=""
+    fi
+
 
     # Update git remotes
     git_remote_update
diff --git a/test-functions.sh b/test-functions.sh
index 92dd60c1..3f181c47 100755
--- a/test-functions.sh
+++ b/test-functions.sh
@@ -398,6 +398,19 @@ function test_periodic {
     assert_equal "${TEST_GIT_CHECKOUTS[glance]}" 'stable/havana'
 }
 
+# Run setup_project without setting a ZUUL_BRANCH which is how a subset of
+# periodic jobs operate
+function test_periodic_no_branch {
+
+    declare -A TEST_GIT_CHECKOUTS
+    declare -A TEST_ZUUL_REF
+    local ZUUL_PROJECT='openstack/glance'
+
+    setup_project openstack/glance 'master'
+
+    assert_equal "${TEST_GIT_CHECKOUTS[glance]}" 'master'
+}
+
 # setup_workspace fails without argument
 function test_workspace_branch_arg {
     assert_raises setup_workspace
@@ -466,6 +479,7 @@ test_multi_branch_on_stable
 test_multi_branch_project_override
 test_one_on_master
 test_periodic
+test_periodic_no_branch
 test_two_on_master
 test_workspace_branch_arg
 test_call_hook_if_defined