diff --git a/helper/config/decode.go b/helper/config/decode.go
index 177f8f930..620198e35 100644
--- a/helper/config/decode.go
+++ b/helper/config/decode.go
@@ -42,6 +42,8 @@ func Decode(target interface{}, config *DecodeOpts, raws ...interface{}) error {
 		if config.InterpolateContext == nil {
 			config.InterpolateContext = ctx
 		} else {
+			config.InterpolateContext.BuildName = ctx.BuildName
+			config.InterpolateContext.BuildType = ctx.BuildType
 			config.InterpolateContext.TemplatePath = ctx.TemplatePath
 			config.InterpolateContext.UserVariables = ctx.UserVariables
 		}
diff --git a/template/interpolate/funcs.go b/template/interpolate/funcs.go
index e5d01b455..75e1344ed 100644
--- a/template/interpolate/funcs.go
+++ b/template/interpolate/funcs.go
@@ -71,7 +71,7 @@ func funcGenBuildName(ctx *Context) interface{} {
 func funcGenBuildType(ctx *Context) interface{} {
 	return func() (string, error) {
 		if ctx == nil || ctx.BuildType == "" {
-			return "", errors.New("build_name not available")
+			return "", errors.New("build_type not available")
 		}
 
 		return ctx.BuildType, nil