diff --git a/lru/lru.go b/lru/lru.go
index f0b67462..40c22ece 100644
--- a/lru/lru.go
+++ b/lru/lru.go
@@ -47,6 +47,8 @@ func NewWithEvictionFunc(size int, f EvictionFunc) *Cache {
 
 // SetEvictionFunc updates the eviction func
 func (c *Cache) SetEvictionFunc(f EvictionFunc) error {
+	c.lock.Lock()
+	defer c.lock.Unlock()
 	if c.cache.OnEvicted != nil {
 		return fmt.Errorf("lru cache eviction function is already set")
 	}