diff --git a/config/validate.go b/config/validate.go
index f7027137..42cb685b 100644
--- a/config/validate.go
+++ b/config/validate.go
@@ -6,23 +6,23 @@ import (
 )
 
 // TODO: use this function from libcompose
-func convertKeysToStrings(item interface{}) interface{} {
+func ConvertKeysToStrings(item interface{}) interface{} {
 	switch typedDatas := item.(type) {
 	case map[string]interface{}:
 		for key, value := range typedDatas {
-			typedDatas[key] = convertKeysToStrings(value)
+			typedDatas[key] = ConvertKeysToStrings(value)
 		}
 		return typedDatas
 	case map[interface{}]interface{}:
 		newMap := make(map[string]interface{})
 		for key, value := range typedDatas {
 			stringKey := key.(string)
-			newMap[stringKey] = convertKeysToStrings(value)
+			newMap[stringKey] = ConvertKeysToStrings(value)
 		}
 		return newMap
 	case []interface{}:
 		for i, value := range typedDatas {
-			typedDatas[i] = append(typedDatas, convertKeysToStrings(value))
+			typedDatas[i] = ConvertKeysToStrings(value)
 		}
 		return typedDatas
 	default:
@@ -35,7 +35,7 @@ func Validate(bytes []byte) (*gojsonschema.Result, error) {
 	if err := yaml.Unmarshal([]byte(bytes), &rawCfg); err != nil {
 		return nil, err
 	}
-	rawCfg = convertKeysToStrings(rawCfg).(map[string]interface{})
+	rawCfg = ConvertKeysToStrings(rawCfg).(map[string]interface{})
 	loader := gojsonschema.NewGoLoader(rawCfg)
 	schemaLoader := gojsonschema.NewStringLoader(schema)
 	return gojsonschema.Validate(schemaLoader, loader)
diff --git a/config/validate_test.go b/config/validate_test.go
index 4cb8c935..ac82bde8 100644
--- a/config/validate_test.go
+++ b/config/validate_test.go
@@ -25,8 +25,19 @@ func testValidate(t *testing.T, cfg []byte, contains string) {
 func TestValidate(t *testing.T) {
 	testValidate(t, []byte("{}"), "")
 	testValidate(t, []byte(`rancher:
-  log: true
-`), "")
+  log: true`), "")
+	testValidate(t, []byte(`write_files:
+- container: console
+  path: /etc/rc.local
+  permissions: "0755"
+  owner: root
+  content: |
+    #!/bin/bash
+    wait-for-docker`), "")
+	testValidate(t, []byte(`rancher:
+  docker:
+    extra_args: ['--insecure-registry', 'my.registry.com']`), "")
+
 	testValidate(t, []byte("bad_key: {}"), "Additional property bad_key is not allowed")
 	testValidate(t, []byte("rancher: []"), "rancher: Invalid type. Expected: object, given: array")