diff --git a/cache.go b/cache.go
index b23880e..7c068f7 100644
--- a/cache.go
+++ b/cache.go
@@ -23,14 +23,13 @@ func (e entry[V]) isExpired() bool {
 // Cache is an in-memory key-value store.
 type Cache[K comparable, V any] struct {
 	data map[K]entry[V]
-	mu   *sync.RWMutex
+	mu   sync.RWMutex
 }
 
 // New instantiate a new cache.
 func New[K comparable, V any]() *Cache[K, V] {
 	return &Cache[K, V]{
 		data: make(map[K]entry[V]),
-		mu:   &sync.RWMutex{},
 	}
 }
 
@@ -47,9 +46,6 @@ func (c *Cache[K, V]) Put(key K, val V) {
 //
 // A 0 ttl value disables the expiration of the value.
 func (c *Cache[K, V]) PutTTL(key K, val V, ttl time.Duration) {
-	c.mu.Lock()
-	defer c.mu.Unlock()
-
 	if ttl == 0 {
 		c.Put(key, val)
 
@@ -58,6 +54,9 @@ func (c *Cache[K, V]) PutTTL(key K, val V, ttl time.Duration) {
 
 	exp := time.Now().Add(ttl)
 
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
 	c.data[key] = entry[V]{&exp, val}
 }