diff --git a/src/Umbraco.Core/Sync/WebServiceServerMessenger.cs b/src/Umbraco.Core/Sync/WebServiceServerMessenger.cs
index c4b3c03d2f..1c63b591b7 100644
--- a/src/Umbraco.Core/Sync/WebServiceServerMessenger.cs
+++ b/src/Umbraco.Core/Sync/WebServiceServerMessenger.cs
@@ -126,8 +126,8 @@ namespace Umbraco.Core.Sync
         public static string GetServerHash(string machineName, string appDomainAppId)
         {
             var hasher = new HashCodeCombiner();
-            hasher.AddCaseInsensitiveString(NetworkHelper.MachineName);
-            hasher.AddCaseInsensitiveString(System.Web.HttpRuntime.AppDomainAppId);
+            hasher.AddCaseInsensitiveString(appDomainAppId);
+            hasher.AddCaseInsensitiveString(machineName);
             return hasher.GetCombinedHashCode();
         }
 
diff --git a/src/Umbraco.Tests/Cache/CacheRefresherTests.cs b/src/Umbraco.Tests/Cache/CacheRefresherTests.cs
index 690ad80525..33dfd16743 100644
--- a/src/Umbraco.Tests/Cache/CacheRefresherTests.cs
+++ b/src/Umbraco.Tests/Cache/CacheRefresherTests.cs
@@ -1,3 +1,4 @@
+using System;
 using NUnit.Framework;
 using Umbraco.Core.Sync;
 using umbraco.presentation.webservices;
@@ -9,16 +10,22 @@ namespace Umbraco.Tests.Cache
     {
         [TestCase("", "123456", "testmachine", true)] //empty hash will continue
         [TestCase("fffffff28449cf33", "123456", "testmachine", false)] //match, don't continue
-        [TestCase("fffffff28449cf33", "12345", "testmachine", true)]
-        [TestCase("fffffff28449cf33", "123456", "testmachin", true)]
-        [TestCase("fffffff28449cf3", "123456", "testmachine", true)]
+        [TestCase("fffffff28449cf33", "12345", "testmachine", true)] // no match, continue
+        [TestCase("fffffff28449cf33", "123456", "testmachin", true)] // same
+        [TestCase("fffffff28449cf3", "123456", "testmachine", true)] // same
         public void Continue_Refreshing_For_Request(string hash, string appDomainAppId, string machineName, bool expected)
         {
             if (expected)
-                Assert.AreEqual(hash, WebServiceServerMessenger.GetServerHash(appDomainAppId, machineName));
+                Assert.IsTrue(Continue(hash, WebServiceServerMessenger.GetServerHash(appDomainAppId, machineName)));
             else
-                Assert.AreNotEqual(hash, WebServiceServerMessenger.GetServerHash(appDomainAppId, machineName));
+                Assert.IsFalse(Continue(hash, WebServiceServerMessenger.GetServerHash(appDomainAppId, machineName)));
         }
 
+        // that's what CacheRefresher.asmx.cs does...
+        private bool Continue(string hash1, string hash2)
+        {
+            if (string.IsNullOrEmpty(hash1)) return true;
+            return hash1 != hash2;
+        }
     }
 }
\ No newline at end of file
diff --git a/src/Umbraco.Web/umbraco.presentation/umbraco/webservices/CacheRefresher.asmx.cs b/src/Umbraco.Web/umbraco.presentation/umbraco/webservices/CacheRefresher.asmx.cs
index 4186b2446a..5cfb8d3393 100644
--- a/src/Umbraco.Web/umbraco.presentation/umbraco/webservices/CacheRefresher.asmx.cs
+++ b/src/Umbraco.Web/umbraco.presentation/umbraco/webservices/CacheRefresher.asmx.cs
@@ -24,6 +24,7 @@ namespace umbraco.presentation.webservices
         // in which case we should ignore the message because it's been processed locally already
         internal static bool SelfMessage(string hash)
         {
+            if (string.IsNullOrEmpty(hash)) return false; // no hash = don't know = not self
             if (hash != WebServiceServerMessenger.GetCurrentServerHash()) return false;
 
             LogHelper.Debug<CacheRefresher>(