diff --git a/oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/nodetype/write/NamedTemplate.java b/oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/nodetype/write/NamedTemplate.java
index c982d4472d..8437405d49 100644
--- a/oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/nodetype/write/NamedTemplate.java
+++ b/oak-core/src/main/java/org/apache/jackrabbit/oak/plugins/nodetype/write/NamedTemplate.java
@@ -16,14 +16,19 @@
  */
 package org.apache.jackrabbit.oak.plugins.nodetype.write;
 
+import java.util.Set;
+
 import javax.annotation.CheckForNull;
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 import javax.jcr.nodetype.ConstraintViolationException;
 
+import org.apache.jackrabbit.JcrConstants;
 import org.apache.jackrabbit.oak.namepath.JcrNameParser;
 import org.apache.jackrabbit.oak.namepath.NameMapper;
 
+import com.google.common.collect.Sets;
+
 /**
  * Abstract base class for the template implementations in this package.
  * Keeps track of the Oak name of this template and provides utility methods
@@ -178,11 +183,19 @@ abstract class NamedTemplate {
     protected String[] getOakNamesOrThrowConstraintViolation(@CheckForNull String[] jcrNames)
             throws ConstraintViolationException {
         if (jcrNames != null) {
-            String[] oakNames = new String[jcrNames.length];
+            boolean hasNtBase = false;
+            Set<String> oakNames = Sets.newHashSetWithExpectedSize(jcrNames.length);
             for (int i = 0; i < jcrNames.length; i++) {
-                oakNames[i] = getOakNameOrThrowConstraintViolation(jcrNames[i]);
+                String n = getOakNameOrThrowConstraintViolation(jcrNames[i]);
+                oakNames.add(n);
+                if (!hasNtBase && JcrConstants.NT_BASE.equals(n)) {
+                    hasNtBase = true;
+                }
+            }
+            if (!hasNtBase) {
+                oakNames.add(JcrConstants.NT_BASE);
             }
-            return oakNames;
+            return oakNames.toArray(new String[] {});
         } else {
             throw new ConstraintViolationException("Missing JCR names");
         }
diff --git a/oak-core/src/test/java/org/apache/jackrabbit/oak/plugins/nodetype/write/NodeTypeRegistryTest.java b/oak-core/src/test/java/org/apache/jackrabbit/oak/plugins/nodetype/write/NodeTypeRegistryTest.java
index 1d82fe0d9c..f4d139d0d5 100644
--- a/oak-core/src/test/java/org/apache/jackrabbit/oak/plugins/nodetype/write/NodeTypeRegistryTest.java
+++ b/oak-core/src/test/java/org/apache/jackrabbit/oak/plugins/nodetype/write/NodeTypeRegistryTest.java
@@ -172,7 +172,6 @@ public class NodeTypeRegistryTest {
 
     }
 
-    @Ignore("OAK-6440")
     @Test
     public void registerNodeType() throws Exception {
         registerNodeType(root, "oak6440-1.cnd");