diff --git a/README.md b/README.md
index 626f64e..fd50fcc 100644
--- a/README.md
+++ b/README.md
@@ -49,6 +49,8 @@ node-cache-manager handles easily and transparently.
         var redis_cache = cache_manager.caching({store: 'redis', db: 1, ttl: 100/*seconds*/});
         var memory_cache = cache_manager.caching({store: 'memory', max: 100, ttl: 10/*seconds*/});
 
+        // Note: callback is optional in set() and del().
+
         redis_cache.set('foo', 'bar', function(err) {
             if (err) { throw err; }
 
diff --git a/lib/stores/memory.js b/lib/stores/memory.js
index 31208f7..13593aa 100644
--- a/lib/stores/memory.js
+++ b/lib/stores/memory.js
@@ -14,7 +14,9 @@ var memory_store = function (args) {
 
     self.set = function (key, value, cb) {
         lru_cache.set(key, value);
-        cb(null);
+        if (cb) {
+            cb(null);
+        }
     };
 
     self.get = function (key, cb) {
@@ -23,7 +25,9 @@ var memory_store = function (args) {
 
     self.del = function (key, cb) {
         lru_cache.del(key);
-        cb(null);
+        if (cb) {
+            cb(null);
+        }
     };
 
     return self;
diff --git a/test/caching.unit.js b/test/caching.unit.js
index 34b1cfe..e185fbe 100644
--- a/test/caching.unit.js
+++ b/test/caching.unit.js
@@ -35,6 +35,16 @@ describe("caching", function () {
                         });
                     });
                 });
+
+                it("lets us set data without a callback", function (done) {
+                    cache.set(key, value);
+                    setTimeout(function () {
+                        cache.get(key, function (err, result) {
+                            assert.equal(result, value);
+                            done();
+                        });
+                    }, 20);
+                });
             });
         });
     });
@@ -66,6 +76,21 @@ describe("caching", function () {
                         });
                     });
                 });
+
+                it("lets us delete data without a callback", function (done) {
+                    cache.get(key, function (err, result) {
+                        assert.equal(result, value);
+
+                        cache.del(key);
+
+                        setTimeout(function () {
+                            cache.get(key, function (err, result) {
+                                assert.ok(!result);
+                                done();
+                            });
+                        }, 20);
+                    });
+                });
             });
         });
     });