diff --git a/src/org/olap4j/mdx/NameSegment.java b/src/org/olap4j/mdx/NameSegment.java
index 16997e9..d2ff3b1 100644
--- a/src/org/olap4j/mdx/NameSegment.java
+++ b/src/org/olap4j/mdx/NameSegment.java
@@ -42,6 +42,9 @@ public NameSegment(
         this.region = region;
         this.name = name;
         this.quoting = quoting;
+        if (name == null) {
+            throw new NullPointerException();
+        }
         if (!(quoting == Quoting.QUOTED || quoting == Quoting.UNQUOTED)) {
             throw new IllegalArgumentException();
         }
diff --git a/testsrc/org/olap4j/mdx/MdxTest.java b/testsrc/org/olap4j/mdx/MdxTest.java
index 23e4864..e785f3f 100644
--- a/testsrc/org/olap4j/mdx/MdxTest.java
+++ b/testsrc/org/olap4j/mdx/MdxTest.java
@@ -133,14 +133,16 @@ public void testIdentifierOfNames() {
             segments.get(2).getQuoting());
 
         assertEquals(
-            "xxx",
+            "[string].[with].[a [bracket]] in it]",
             identifierNode.toString());
 
-        // Empty array is valid. (I don't feel strongly about this.)
-        identifierNode =
-            IdentifierNode.ofNames();
-        assertEquals(0, identifierNode.getSegmentList().size());
-        assertEquals("", identifierNode.toString());
+        // Empty array is invalid.
+        try {
+            identifierNode = IdentifierNode.ofNames();
+            fail("expected error, got " + identifierNode);
+        } catch (IllegalArgumentException e) {
+            // ok
+        }
 
         // Array containing null is not valid.
         try {