diff --git a/source/java/org/alfresco/repo/dictionary/ModelValidatorImpl.java b/source/java/org/alfresco/repo/dictionary/ModelValidatorImpl.java
index c74aa1071a..ea039ffe6c 100644
--- a/source/java/org/alfresco/repo/dictionary/ModelValidatorImpl.java
+++ b/source/java/org/alfresco/repo/dictionary/ModelValidatorImpl.java
@@ -1,31 +1,30 @@
-/*
- * #%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.dictionary;
 
-import java.util.ArrayList;
 import java.util.Collection;
 import java.util.HashSet;
 import java.util.List;
@@ -46,7 +45,7 @@ import org.alfresco.service.cmr.dictionary.AspectDefinition;
 import org.alfresco.service.cmr.dictionary.ClassDefinition;
 import org.alfresco.service.cmr.dictionary.ConstraintDefinition;
 import org.alfresco.service.cmr.dictionary.DictionaryException;
-import org.alfresco.service.cmr.dictionary.DictionaryService;
+import org.alfresco.service.cmr.dictionary.DictionaryService;
 import org.alfresco.service.cmr.dictionary.ModelDefinition;
 import org.alfresco.service.cmr.dictionary.NamespaceDefinition;
 import org.alfresco.service.cmr.dictionary.PropertyDefinition;
@@ -73,7 +72,7 @@ public class ModelValidatorImpl implements ModelValidator
     private static final Log logger = LogFactory.getLog(ModelValidatorImpl.class);
 
     private DictionaryDAO dictionaryDAO;
-    private DictionaryService dictionaryService;
+    private DictionaryService dictionaryService;
     private QNameDAO qnameDAO;
     private NamespaceService namespaceService;
     private TransactionService transactionService;
@@ -122,11 +121,11 @@ public class ModelValidatorImpl implements ModelValidator
         this.tenantAdminService = tenantAdminService;
     }
 
-    public void setDictionaryService(DictionaryService dictionaryService)
-    {
-        this.dictionaryService = dictionaryService;
-    }
-
+    public void setDictionaryService(DictionaryService dictionaryService)
+    {
+        this.dictionaryService = dictionaryService;
+    }
+
     private void checkCustomModelNamespace(M2Model model, String tenantDomain)
     {
         if(tenantDomain != null && !tenantDomain.equals("") && enforceTenantInNamespace)
@@ -477,7 +476,16 @@ public class ModelValidatorImpl implements ModelValidator
                 }
                 else
                 {
-                    throw new AlfrescoRuntimeException("Failed to validate model update - found deleted " + modelDiff.getElementType() + " '" + modelDiff.getElementName() + "'");
+                    /*
+                     * As the M2Model#compile method will detect and throw exception for any missing namespace which
+                     * is required to define any Type, Aspect or Property, we can safely add this extra check.
+                     * See APPSREPO-59 comment for details.
+                     */
+                    if (!modelDiff.getElementType().equals(M2ModelDiff.TYPE_NAMESPACE))
+                    {
+                        throw new AlfrescoRuntimeException("Failed to validate model update - found deleted " + modelDiff.getElementType() + " '" + modelDiff
+                                                .getElementName() + "'");
+                    }
                 }
             }
 
@@ -485,37 +493,37 @@ public class ModelValidatorImpl implements ModelValidator
             {
                 throw new AlfrescoRuntimeException("Failed to validate model update - found non-incrementally updated " + modelDiff.getElementType() + " '" + modelDiff.getElementName() + "'");
             }
-
-            if(modelDiff.getDiffType().equals(M2ModelDiff.DIFF_CREATED))
-            {
-                if (modelDiff.getElementType().equals(M2ModelDiff.TYPE_NAMESPACE))
-                {
-                    ModelDefinition importedModel = dictionaryService.getModelByNamespaceUri(modelDiff.getNamespaceDefinition().getUri());
-                    if(importedModel != null && !model.getNamespaces().isEmpty())
-                    {
-                        checkCircularDependency(importedModel, model, importedModel.getName().getLocalName());
-                    }
-                }
-            }
+
+            if(modelDiff.getDiffType().equals(M2ModelDiff.DIFF_CREATED))
+            {
+                if (modelDiff.getElementType().equals(M2ModelDiff.TYPE_NAMESPACE))
+                {
+                    ModelDefinition importedModel = dictionaryService.getModelByNamespaceUri(modelDiff.getNamespaceDefinition().getUri());
+                    if(importedModel != null && !model.getNamespaces().isEmpty())
+                    {
+                        checkCircularDependency(importedModel, model, importedModel.getName().getLocalName());
+                    }
+                }
+            }
         }
         
         // TODO validate that any deleted constraints are not being referenced - else currently will become anon - or push down into model compilation (check backwards compatibility ...)
     }
-
-    private void checkCircularDependency(ModelDefinition model, M2Model existingModel, String parentPrefixedName) throws AlfrescoRuntimeException
-    {
-        for (NamespaceDefinition importedNamespace : model.getImportedNamespaces())
-        {
-            ModelDefinition md = null;
-            if ((md = dictionaryService.getModelByNamespaceUri(importedNamespace.getUri())) != null)
-            {
-                if (existingModel.getNamespace(importedNamespace.getUri()) != null)
-                {
-                    throw new AlfrescoRuntimeException("Failed to validate model update - found circular dependency. You can't set parent " + parentPrefixedName + " as it's model already depends on " + existingModel.getName());
-                }
-                checkCircularDependency(md, existingModel, parentPrefixedName);
-            }
-        }
-    }
-
+
+    private void checkCircularDependency(ModelDefinition model, M2Model existingModel, String parentPrefixedName) throws AlfrescoRuntimeException
+    {
+        for (NamespaceDefinition importedNamespace : model.getImportedNamespaces())
+        {
+            ModelDefinition md = null;
+            if ((md = dictionaryService.getModelByNamespaceUri(importedNamespace.getUri())) != null)
+            {
+                if (existingModel.getNamespace(importedNamespace.getUri()) != null)
+                {
+                    throw new AlfrescoRuntimeException("Failed to validate model update - found circular dependency. You can't set parent " + parentPrefixedName + " as it's model already depends on " + existingModel.getName());
+                }
+                checkCircularDependency(md, existingModel, parentPrefixedName);
+            }
+        }
+    }
+
 }
diff --git a/source/test-java/org/alfresco/repo/dictionary/ModelValidatorTest.java b/source/test-java/org/alfresco/repo/dictionary/ModelValidatorTest.java
index e3010bf88e..4ea0766750 100644
--- a/source/test-java/org/alfresco/repo/dictionary/ModelValidatorTest.java
+++ b/source/test-java/org/alfresco/repo/dictionary/ModelValidatorTest.java
@@ -1,28 +1,28 @@
-/*
- * #%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.dictionary;
 
 import static org.junit.Assert.assertNotNull;
@@ -37,6 +37,7 @@ import org.alfresco.repo.domain.qname.QNameDAO;
 import org.alfresco.repo.node.archive.NodeArchiveService;
 import org.alfresco.repo.security.authentication.AuthenticationUtil;
 import org.alfresco.repo.transaction.RetryingTransactionHelper.RetryingTransactionCallback;
+import org.alfresco.service.cmr.dictionary.DictionaryException;
 import org.alfresco.service.cmr.model.FileFolderService;
 import org.alfresco.service.cmr.model.FileInfo;
 import org.alfresco.service.cmr.repository.ContentService;
@@ -50,6 +51,7 @@ import org.alfresco.service.namespace.QName;
 import org.alfresco.service.transaction.TransactionService;
 import org.alfresco.util.ApplicationContextHelper;
 import org.alfresco.util.GUID;
+import org.junit.AfterClass;
 import org.junit.Before;
 import org.junit.Test;
 import org.springframework.context.ApplicationContext;
@@ -102,6 +104,12 @@ public class ModelValidatorTest
         addModel();
     }
 
+    @AfterClass
+    public static void cleanUp()
+    {
+        AuthenticationUtil.clearCurrentSecurityContext();
+    }
+
     private QName addModel()
     {
         this.testNamespace = "http://www.alfresco.org/test/" + modelName;
@@ -449,4 +457,54 @@ public class ModelValidatorTest
         };
         transactionService.getRetryingTransactionHelper().doInTransaction(deleteModelAgainCallback, false, true);
     }
+
+    /**
+     * Tests that an unused imported namespace can be deleted.
+     *
+     * @throws Exception
+     */
+    @Test
+    public void testDeleteNamespace() throws Exception
+    {
+        // authenticate
+        AuthenticationUtil.pushAuthentication();
+        AuthenticationUtil.setFullyAuthenticatedUser(AuthenticationUtil.getAdminUserName());
+
+        // Remove the only property (created in setup method)
+        this.type.removeProperty(this.property.getName());
+        // We don't have any property that references the imported dictionary namespace, so remove it.
+        this.model.removeImport(NamespaceService.DICTIONARY_MODEL_1_0_URI);
+
+        // Check that it compiles
+        CompiledModel compiledModel = model.compile(dictionaryDAO, namespaceDAO, true);
+        modelValidator.validateModel(compiledModel);
+
+        // Remove the imported content model namespace
+        this.model.removeImport(NamespaceService.CONTENT_MODEL_1_0_URI);
+        try
+        {
+            model.compile(dictionaryDAO, namespaceDAO, true);
+            fail("Should have failed as the model's type references the content model (cm:folder).");
+        }
+        catch (DictionaryException dx)
+        {
+            //expected
+        }
+
+        // Add the content model namespace back
+        model.createImport(NamespaceService.CONTENT_MODEL_1_0_URI, NamespaceService.CONTENT_MODEL_PREFIX);
+        model.compile(dictionaryDAO, namespaceDAO, true);
+
+        // Remove the defined namespace
+        this.model.removeNamespace(testNamespace);
+        try
+        {
+            model.compile(dictionaryDAO, namespaceDAO, true);
+            fail("Should have failed as the type's name references the namespace.");
+        }
+        catch (DictionaryException dx)
+        {
+            //expected
+        }
+    }
 }