1 files changed, 11 insertions, 0 deletions
diff --git a/reachability/domain.go b/reachability/domain.go
index 9fcf721e..1fe24fe8 100644
--- a/reachability/domain.go
+++ b/reachability/domain.go
@@ -1,5 +1,7 @@
 package reachability
 
+import "fmt"
+
 // Domain specifies which graph edges are traversed.
 type Domain uint8
 
@@ -9,3 +11,12 @@ const (
 	// DomainObjects traverses full commit/tree/blob objects.
 	DomainObjects
 )
+
+func validateDomain(domain Domain) error {
+	switch domain {
+	case DomainCommits, DomainObjects:
+		return nil
+	default:
+		return fmt.Errorf("reachability: invalid domain %d", domain)
+	}
+}