diff --git a/ActiveSync/SOGoActiveSyncDispatcher+Sync.m b/ActiveSync/SOGoActiveSyncDispatcher+Sync.m
index 23c13fe1e..0f16be544 100644
--- a/ActiveSync/SOGoActiveSyncDispatcher+Sync.m
+++ b/ActiveSync/SOGoActiveSyncDispatcher+Sync.m
@@ -2599,9 +2599,36 @@ FIXME
   // We enter our loop detection change
   for (i = 0; i < (heartbeatInterval/internalInterval); i++)
     {
+      // Terminate the process if we need to
       if ([self easShouldTerminate])
         break;
 
+      // We first check of any of the collections we want to sync are already
+      // in an other sync process. If that's the case, we do not do anything
+      // and we return immediately. So we'll let the other sync process terminate
+      for (j = 0; j < [allCollections count]; j++)
+        {
+          aCollection = [allCollections objectAtIndex: j];
+          globalMetadata = [self globalMetadataForDevice];
+
+          key = [NSString stringWithFormat: @"SyncRequest+%@", [[[(id)[aCollection getElementsByTagName: @"CollectionId"] lastObject] textValue] stringByUnescapingURL]];
+
+          if (!([[globalMetadata objectForKey: key] isEqual: processIdentifier]))
+            {
+              if (debugOn)
+                [self logWithFormat: @"EAS - Discard response %@", [self globalMetadataForDevice]];
+
+              [output appendString: @"<Status>13</Status>"];
+              [output appendString: @"</Sync>"];
+              d = [[output dataUsingEncoding: NSUTF8StringEncoding] xml2wbxml];
+              [theResponse setContent: d];
+              RELEASE(output);
+              return;
+            }
+
+        }
+
+      // We're good to go to sync the collections
       s = [NSMutableString string];
 
       for (j = 0; j < [allCollections count]; j++)
@@ -2613,21 +2640,6 @@ FIXME
                        changeDetected: &changeDetected
                   maxSyncResponseSize: maxSyncResponseSize];
 
-          // Don't return a response if another Sync is waiting.
-          globalMetadata = [self globalMetadataForDevice];
-          key = [NSString stringWithFormat: @"SyncRequest+%@", [[[(id)[aCollection getElementsByTagName: @"CollectionId"] lastObject] textValue] stringByUnescapingURL]];
-
-          if (!([[globalMetadata objectForKey: key] isEqual: processIdentifier]))
-            {
-              if (debugOn)
-                [self logWithFormat: @"EAS - Discard response %@", [self globalMetadataForDevice]];
-
-              [theResponse setStatus: 503];
-
-              RELEASE(output);
-              return;
-            }
-
           if ((maxSyncResponseSize > 0 && [s length] >= maxSyncResponseSize))
             break;
         }
diff --git a/NEWS b/NEWS
index 3dbfc6995..5f4daaa88 100644
--- a/NEWS
+++ b/NEWS
@@ -5,6 +5,7 @@ Bug fixes
  - [core] properly update the last-modified attribute (#4313)
  - [web] prevent deletion of special folders using del key
  - [eas] improved alarms syncing with EAS devices (#4351)
+ - [eas] avoid potential cache update when breaking sync queries (#4422)
 
 4.0.0 (2018-03-07)
 ------------------