diff --git a/cache/memory/memory.go b/cache/memory/memory.go
index 045d2237..28a9e8f4 100644
--- a/cache/memory/memory.go
+++ b/cache/memory/memory.go
@@ -139,7 +139,7 @@ func (c *Cache) Expired() int {
 
 // Set adds or updates item in cache
 func (c *Cache) Set(key string, data any, expiration ...time.Duration) bool {
-	if c == nil {
+	if c == nil || data == nil {
 		return false
 	}
 
@@ -279,11 +279,11 @@ func (c *Cache) Flush() bool {
 // Validate validates cache configuration
 func (c Config) Validate() error {
 	if c.DefaultExpiration < MIN_EXPIRATION {
-		return errors.New("Expiration is too short (< 1ms)")
+		return errors.New("Invalid configuration: Expiration is too short (< 1ms)")
 	}
 
 	if c.CleanupInterval != 0 && c.CleanupInterval < MIN_CLEANUP_INTERVAL {
-		return errors.New("Cleanup interval is too short (< 1ms)")
+		return errors.New("Invalid configuration: Cleanup interval is too short (< 1ms)")
 	}
 
 	return nil
diff --git a/cache/memory/memory_test.go b/cache/memory/memory_test.go
index e2690d7b..351d6840 100644
--- a/cache/memory/memory_test.go
+++ b/cache/memory/memory_test.go
@@ -66,7 +66,7 @@ func (s *CacheSuite) TestCache(c *C) {
 	c.Assert(cache.Get("2"), Equals, nil)
 	c.Assert(item, Equals, nil)
 
-	cache.Flush()
+	c.Assert(cache.Flush(), Equals, true)
 }
 
 func (s *CacheSuite) TestCacheWithoutJanitor(c *C) {
@@ -135,9 +135,9 @@ func (s *CacheSuite) TestNil(c *C) {
 func (s *CacheSuite) TestConfig(c *C) {
 	_, err := New(Config{DefaultExpiration: 1})
 
-	c.Assert(err.Error(), Equals, "Expiration is too short (< 1ms)")
+	c.Assert(err.Error(), Equals, "Invalid configuration: Expiration is too short (< 1ms)")
 
 	_, err = New(Config{DefaultExpiration: time.Minute, CleanupInterval: 1})
 
-	c.Assert(err.Error(), Equals, "Cleanup interval is too short (< 1ms)")
+	c.Assert(err.Error(), Equals, "Invalid configuration: Cleanup interval is too short (< 1ms)")
 }