diff --git a/make.go b/make.go
index c2c222c..538c7e0 100644
--- a/make.go
+++ b/make.go
@@ -12,7 +12,7 @@ func Make(conf Config) (string, error) {
 	}
 
 	if conf.prefix != "" {
-		conf.prefix = conf.prefix + conf.separator
+		conf.prefix += conf.separator
 	}
 	if conf.original != "" {
 		conf.original = conf.separator + conf.original
diff --git a/make_test.go b/make_test.go
index 28096ce..ffdecee 100644
--- a/make_test.go
+++ b/make_test.go
@@ -36,7 +36,9 @@ func TestMake(t *testing.T) {
 
 	for _, testcase := range testcases {
 		t.Run(testcase.name, func(sub *testing.T) {
-			opts := append(testcase.opts, genOpt)
+			opts := testcase.opts
+			opts = append(opts, genOpt)
+
 			conf := NewConfig(opts...)
 			st, err := Make(conf)
 			assert.NoError(t, err)