diff --git a/command/output.go b/command/output.go
index c40b94e3c9..40cdd10a57 100644
--- a/command/output.go
+++ b/command/output.go
@@ -137,7 +137,8 @@ func (c *OutputCommand) Run(args []string) int {
 			return 1
 		}
 	default:
-		panic(fmt.Errorf("Unknown output type: %T", v.Value.(string)))
+		c.Ui.Error(fmt.Sprintf("Unknown output type: %T", v.Type))
+		return 1
 	}
 
 	return 0