diff --git a/activesupport/CHANGELOG.md b/activesupport/CHANGELOG.md
index 19db8ac8736a59c47d27c010dfc5b1e627b2891f..973eaef471443f23a32cfe3067524674cce9fef5 100644
--- a/activesupport/CHANGELOG.md
+++ b/activesupport/CHANGELOG.md
@@ -1,3 +1,7 @@
+*   MemCacheStore should only accept a Dalli::Client, or create one.
+
+    *arthurnn*
+
 *   Don't lazy load the `tzinfo` library as it causes problems on Windows.
 
     Fixes #13553
diff --git a/activesupport/lib/active_support/cache/mem_cache_store.rb b/activesupport/lib/active_support/cache/mem_cache_store.rb
index 1ac4819d47bb8fd1a0dd6e9b9713926678683ac5..0eacc4c07887a22a1fffdba44495041418dcea50 100644
--- a/activesupport/lib/active_support/cache/mem_cache_store.rb
+++ b/activesupport/lib/active_support/cache/mem_cache_store.rb
@@ -46,6 +46,9 @@ def initialize(*addresses)
         options = addresses.extract_options!
         super(options)
 
+        unless [String, Dalli::Client, NilClass].include?(addresses.first.class)
+          raise ArgumentError, "First argument must be an empty array, an array of hosts or a Dalli::Client instance."
+        end
         if addresses.first.is_a?(Dalli::Client)
           @data = addresses.first
         else
diff --git a/activesupport/test/caching_test.rb b/activesupport/test/caching_test.rb
index 09781f3e7ae7c5a7bdcb3adebcfe883236782ab6..7fd76ddf8b66e5940295d903547f5b2524399c25 100644
--- a/activesupport/test/caching_test.rb
+++ b/activesupport/test/caching_test.rb
@@ -110,6 +110,14 @@ def test_mem_cache_fragment_cache_store_with_given_mem_cache
     assert_kind_of(ActiveSupport::Cache::MemCacheStore, store)
   end
 
+  def test_mem_cache_fragment_cache_store_with_not_dalli_client
+    Dalli::Client.expects(:new).never
+    memcache = Object.new
+    assert_raises(ArgumentError) do
+      ActiveSupport::Cache.lookup_store :mem_cache_store, memcache
+    end
+  end
+
   def test_mem_cache_fragment_cache_store_with_multiple_servers
     Dalli::Client.expects(:new).with(%w[localhost 192.168.1.1], {})
     store = ActiveSupport::Cache.lookup_store :mem_cache_store, "localhost", '192.168.1.1'