diff --git a/packer/environment.go b/packer/environment.go
index 0cbb8a95bdb6eb800204905b8d80d89ba2bf19f9..ee6f443fe3473a1f87a4dd6c5e980e5c2f1bfe3b 100644
--- a/packer/environment.go
+++ b/packer/environment.go
@@ -245,7 +245,7 @@ func (e *coreEnvironment) Cli(args []string) (result int, err error) {
 
 		// If we still don't have a command, show the help.
 		if command == nil {
-			log.Printf("Environment.CLI: command not found: %s\n", args[0])
+			e.ui.Error(fmt.Sprintf("Unknown command: %s\n", args[0]))
 			e.printHelp()
 			return 1, nil
 		}