diff --git a/commands.go b/commands.go
index c889d37f1..d726e8ae0 100644
--- a/commands.go
+++ b/commands.go
@@ -46,11 +46,6 @@ var HiddenCommands map[string]struct{}
 // Ui is the cli.Ui used for communicating to the outside world.
 var Ui cli.Ui
 
-const (
-	ErrorPrefix  = "e:"
-	OutputPrefix = "o:"
-)
-
 func initCommands(
 	originalWorkingDir string,
 	config *cliconfig.Config,
diff --git a/synchronized_writers.go b/synchronized_writers.go
deleted file mode 100644
index 2533d1316..000000000
--- a/synchronized_writers.go
+++ /dev/null
@@ -1,31 +0,0 @@
-package main
-
-import (
-	"io"
-	"sync"
-)
-
-type synchronizedWriter struct {
-	io.Writer
-	mutex *sync.Mutex
-}
-
-// synchronizedWriters takes a set of writers and returns wrappers that ensure
-// that only one write can be outstanding at a time across the whole set.
-func synchronizedWriters(targets ...io.Writer) []io.Writer {
-	mutex := &sync.Mutex{}
-	ret := make([]io.Writer, len(targets))
-	for i, target := range targets {
-		ret[i] = &synchronizedWriter{
-			Writer: target,
-			mutex:  mutex,
-		}
-	}
-	return ret
-}
-
-func (w *synchronizedWriter) Write(p []byte) (int, error) {
-	w.mutex.Lock()
-	defer w.mutex.Unlock()
-	return w.Writer.Write(p)
-}