diff --git a/github/interface.go b/github/interface.go
index 901a5b6..d5ed7a2 100644
--- a/github/interface.go
+++ b/github/interface.go
@@ -32,5 +32,5 @@ type RepoAssignee struct {
 }
 
 func (i *GitHubInfo) Key() string {
-	return i.RepositoryID + ":" + i.LocalBranch
+	return i.RepositoryID + "_" + i.LocalBranch
 }
diff --git a/spr/spr.go b/spr/spr.go
index b741ea8..2e3abb9 100644
--- a/spr/spr.go
+++ b/spr/spr.go
@@ -267,7 +267,9 @@ func (sd *stackediff) MergePullRequests(ctx context.Context, count *uint) {
 			lastCommit := localCommits[len(localCommits)-1]
 			checkedCommit, found := sd.config.Internal.MergeCheckCommit[githubInfo.Key()]
 
-			if !found || checkedCommit == "SKIP" || lastCommit.CommitHash != checkedCommit {
+			if !found {
+				check(errors.New("need to run merge check 'spr check' before merging"))
+			} else if checkedCommit != "SKIP" && lastCommit.CommitHash != checkedCommit {
 				check(errors.New("need to run merge check 'spr check' before merging"))
 			}
 		}