diff --git a/git-codereview/branch.go b/git-codereview/branch.go
index 5d47dc9..13193ff 100644
--- a/git-codereview/branch.go
+++ b/git-codereview/branch.go
@@ -307,6 +307,9 @@
 	if !b.HasPendingCommit() {
 		return nil, fmt.Errorf("no changes pending")
 	}
+	if c.ChangeID == "" {
+		return nil, fmt.Errorf("missing Change-Id")
+	}
 	id := fullChangeID(b, c)
 	for i, x := range extra {
 		if i == 0 {