diff --git a/common/collect/string_list.go b/common/collect/string_list.go
index 498f50eca..528c213e9 100644
--- a/common/collect/string_list.go
+++ b/common/collect/string_list.go
@@ -7,6 +7,6 @@ func NewStringList(raw []string) *StringList {
 	return &list
 }
 
-func (this *StringList) Len() int {
-	return len(*this)
+func (this StringList) Len() int {
+	return len(this)
 }
diff --git a/common/collect/string_list_json_test.go b/common/collect/string_list_json_test.go
index beb3d0690..ca2fdc119 100644
--- a/common/collect/string_list_json_test.go
+++ b/common/collect/string_list_json_test.go
@@ -18,3 +18,13 @@ func TestStringListUnmarshalError(t *testing.T) {
 	err := json.Unmarshal([]byte(rawJson), list)
 	assert.Error(err).IsNotNil()
 }
+
+func TestStringListLen(t *testing.T) {
+	assert := assert.On(t)
+
+	rawJson := `"a, b, c, d"`
+	list := new(StringList)
+	err := json.Unmarshal([]byte(rawJson), list)
+	assert.Error(err).IsNil()
+	assert.Int(list.Len()).Equals(4)
+}