diff --git a/src/main/java/org/alfresco/repo/node/UndeletableAspect.java b/src/main/java/org/alfresco/repo/node/UndeletableAspect.java
index 1396c38f9b..c2ce8dabfa 100644
--- a/src/main/java/org/alfresco/repo/node/UndeletableAspect.java
+++ b/src/main/java/org/alfresco/repo/node/UndeletableAspect.java
@@ -1,32 +1,36 @@
-/*
- * #%L
- * Alfresco Repository
- * %%
- * Copyright (C) 2005 - 2016 Alfresco Software Limited
- * %%
- * This file is part of the Alfresco software. 
- * If the software was purchased under a paid Alfresco license, the terms of 
- * the paid license agreement will prevail.  Otherwise, the software is 
- * provided under the following open source license terms:
- * 
- * Alfresco is free software: you can redistribute it and/or modify
- * it under the terms of the GNU Lesser General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * (at your option) any later version.
- * 
- * Alfresco is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU Lesser General Public License for more details.
- * 
- * You should have received a copy of the GNU Lesser General Public License
- * along with Alfresco. If not, see <http://www.gnu.org/licenses/>.
- * #L%
- */
+/*
+ * #%L
+ * Alfresco Repository
+ * %%
+ * Copyright (C) 2005 - 2016 Alfresco Software Limited
+ * %%
+ * This file is part of the Alfresco software. 
+ * If the software was purchased under a paid Alfresco license, the terms of 
+ * the paid license agreement will prevail.  Otherwise, the software is 
+ * provided under the following open source license terms:
+ * 
+ * Alfresco is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ * 
+ * Alfresco is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ * 
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with Alfresco. If not, see <http://www.gnu.org/licenses/>.
+ * #L%
+ */
 package org.alfresco.repo.node;
 
 import org.alfresco.error.AlfrescoRuntimeException;
 import org.alfresco.model.ContentModel;
+import org.alfresco.repo.copy.CopyBehaviourCallback;
+import org.alfresco.repo.copy.CopyDetails;
+import org.alfresco.repo.copy.CopyServicePolicies;
+import org.alfresco.repo.copy.DoNothingCopyBehaviourCallback;
 import org.alfresco.repo.node.NodeServicePolicies;
 import org.alfresco.repo.node.NodeServicePolicies.BeforeDeleteNodePolicy;
 import org.alfresco.repo.policy.Behaviour;
@@ -35,6 +39,7 @@ import org.alfresco.repo.policy.PolicyComponent;
 import org.alfresco.service.cmr.repository.NodeRef;
 import org.alfresco.service.cmr.repository.NodeService;
 import org.alfresco.service.cmr.site.SiteService;
+import org.alfresco.service.namespace.NamespaceService;
 import org.alfresco.service.namespace.QName;
 
 /**
@@ -54,7 +59,8 @@ import org.alfresco.service.namespace.QName;
  * @author Neil Mc Erlean
  * @since 3.5.0
  */
-public class UndeletableAspect implements NodeServicePolicies.BeforeDeleteNodePolicy
+public class UndeletableAspect implements NodeServicePolicies.BeforeDeleteNodePolicy,
+        CopyServicePolicies.OnCopyNodePolicy
 {
    private PolicyComponent policyComponent;
    private NodeService nodeService;
@@ -87,6 +93,11 @@ public class UndeletableAspect implements NodeServicePolicies.BeforeDeleteNodePo
        this.policyComponent.bindClassBehaviour(BeforeDeleteNodePolicy.QNAME,
                ContentModel.ASPECT_UNDELETABLE,
                new JavaBehaviour(this, "beforeDeleteNode", Behaviour.NotificationFrequency.EVERY_EVENT));
+
+       policyComponent.bindClassBehaviour(
+               QName.createQName(NamespaceService.ALFRESCO_URI, "getCopyCallback"),
+               ContentModel.ASPECT_UNDELETABLE,
+               new JavaBehaviour(this, "getCopyCallback"));
    }
 
    /**
@@ -98,4 +109,10 @@ public class UndeletableAspect implements NodeServicePolicies.BeforeDeleteNodePo
         QName nodeType = nodeService.getType(nodeRef);
         throw new AlfrescoRuntimeException(nodeType.toPrefixString() + " deletion is not allowed. Attempted to delete " + nodeRef);
     }
+
+    @Override
+    public CopyBehaviourCallback getCopyCallback(QName classRef, CopyDetails copyDetails)
+    {
+        return DoNothingCopyBehaviourCallback.getInstance();
+    }
 }
diff --git a/src/test/java/org/alfresco/repo/coci/CheckOutCheckInServiceImplTest.java b/src/test/java/org/alfresco/repo/coci/CheckOutCheckInServiceImplTest.java
index dbbe147aaa..e7958c356f 100644
--- a/src/test/java/org/alfresco/repo/coci/CheckOutCheckInServiceImplTest.java
+++ b/src/test/java/org/alfresco/repo/coci/CheckOutCheckInServiceImplTest.java
@@ -1047,6 +1047,29 @@ public class CheckOutCheckInServiceImplTest extends BaseSpringTest
             fail("Lockable aspect should not be copied from the working copy to the original document");
         }
     }
+
+    public void testCanCheckInWhenOriginalHasUndeletableAspect()
+    {
+        nodeService.addAspect(nodeRef, ContentModel.ASPECT_UNDELETABLE, null);
+        // Pre-condition of test, original must have sys:undeletable
+        assertTrue(nodeService.hasAspect(nodeRef, ContentModel.ASPECT_UNDELETABLE));
+
+        // Check-out nodeRef
+        NodeRef workingCopy = this.cociService.checkout(
+                this.nodeRef,
+                this.rootNodeRef,
+                ContentModel.ASSOC_CHILDREN,
+                QName.createQName("workingCopy"));
+        assertNotNull(workingCopy);
+
+        // Check that the working copy does not have the sys:undeletable aspect
+        assertFalse(nodeService.hasAspect(workingCopy, ContentModel.ASPECT_UNDELETABLE));
+
+        // Check-in: must work despite original having the sys:undeletable aspect (MNT-18546)
+        Map<String, Serializable> versionProperties = new HashMap<String, Serializable>();
+        versionProperties.put(Version.PROP_DESCRIPTION, "This is a test version");
+        cociService.checkin(workingCopy, versionProperties);
+    }
     
     private NodeRef createFolderWithPermission(NodeRef parent, String username, String permission)
     {