diff --git a/entry.go b/entry.go
index 7e2c899..b3a8082 100644
--- a/entry.go
+++ b/entry.go
@@ -113,6 +113,8 @@ func (entry *Entry) WithField(key string, value interface{}) *Entry {
 
 // Add a map of fields to the Entry.
 func (entry *Entry) WithFields(fields Fields) *Entry {
+	entry.Logger.mu.Lock()
+	defer entry.Logger.mu.Unlock()
 	data := make(Fields, len(entry.Data)+len(fields))
 	for k, v := range entry.Data {
 		data[k] = v
diff --git a/entry_test.go b/entry_test.go
index f764085..e1cb1b5 100644
--- a/entry_test.go
+++ b/entry_test.go
@@ -134,7 +134,7 @@ func TestEntryWithIncorrectField(t *testing.T) {
 
 	fn := func() {}
 
-	e := Entry{}
+	e := &Entry{Logger: New()}
 	eWithFunc := e.WithFields(Fields{"func": fn})
 	eWithFuncPtr := e.WithFields(Fields{"funcPtr": &fn})
 
@@ -162,8 +162,8 @@ func TestEntryLogfLevel(t *testing.T) {
 	entry := NewEntry(logger)
 
 	entry.Logf(DebugLevel, "%s", "debug")
-	assert.NotContains(t, buffer.String(), "debug", )
+	assert.NotContains(t, buffer.String(), "debug")
 
 	entry.Logf(WarnLevel, "%s", "warn")
-	assert.Contains(t, buffer.String(), "warn", )
-}
\ No newline at end of file
+	assert.Contains(t, buffer.String(), "warn")
+}