diff --git a/daemon/cluster/services.go b/daemon/cluster/services.go
index ff1300f2d1..2f8437ce5f 100644
--- a/daemon/cluster/services.go
+++ b/daemon/cluster/services.go
@@ -562,6 +562,8 @@ func (c *Cluster) ServiceLogs(ctx context.Context, selector *backend.LogSelector
 					m.Source = "stdout"
 				case swarmapi.LogStreamStderr:
 					m.Source = "stderr"
+				default:
+					// TODO(thaJeztah): make switch exhaustive; add swarmapi.LogStreamUnknown
 				}
 				m.Line = msg.Data