@@ -29,17 +29,17 @@ import (

 )

 // Environment variable interpolation will happen on these statements only.

-var replaceEnvAllowed = map[string]struct{}{

-	command.Env:        {},

-	command.Label:      {},

-	command.Add:        {},

-	command.Copy:       {},

-	command.Workdir:    {},

-	command.Expose:     {},

-	command.Volume:     {},

-	command.User:       {},

-	command.StopSignal: {},

-	command.Arg:        {},

+var replaceEnvAllowed = map[string]bool{

+	command.Env:        true,

+	command.Label:      true,

+	command.Add:        true,

+	command.Copy:       true,

+	command.Workdir:    true,

+	command.Expose:     true,

+	command.Volume:     true,

+	command.User:       true,

+	command.StopSignal: true,

+	command.Arg:        true,

 }

 // Certain commands are allowed to have their args split into more

@@ -163,11 +163,11 @@ func (b *Builder) dispatch(stepN int, ast *parser.Node) error {

 		ast = ast.Next

 		var str string

 		str = ast.Value

-		if _, ok := replaceEnvAllowed[cmd]; ok {

+		if replaceEnvAllowed[cmd] {

 			var err error

 			var words []string

-			if _, ok := allowWordExpansion[cmd]; ok {

+			if allowWordExpansion[cmd] {

 				words, err = ProcessWords(str, envs)

 				if err != nil {

 					return err