diff --git a/src/lib.rs b/src/lib.rs
index ee0b818..ac47f47 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -407,8 +407,8 @@ impl<K: Clone + Eq + Hash, V, S: BuildHasher, W: WeightScale<K, V>> CLruCache<K,
     }
 
     /// Returns a bool indicating whether the given key is in the cache.
-    /// Does not update the LRU list.
-    pub fn contains<Q>(&mut self, key: &Q) -> bool
+    /// Like `peek`, `contains` does not update the LRU list so the key's position will be unchanged.
+    pub fn contains<Q>(&self, key: &Q) -> bool
     where
         K: Borrow<Q>,
         Q: Hash + Eq + ?Sized,