diff --git a/org.eclipse.xtext.tests/src/org/eclipse/xtext/naming/DeclarativeQualifiedNameConverterTest.java b/org.eclipse.xtext.tests/src/org/eclipse/xtext/naming/DeclarativeQualifiedNameConverterTest.java
index 3a3014a17..c67c3e764 100644
--- a/org.eclipse.xtext.tests/src/org/eclipse/xtext/naming/DeclarativeQualifiedNameConverterTest.java
+++ b/org.eclipse.xtext.tests/src/org/eclipse/xtext/naming/DeclarativeQualifiedNameConverterTest.java
@@ -8,12 +8,16 @@
 package org.eclipse.xtext.naming;
 
 import org.junit.Assert;
+import org.junit.Rule;
 import org.junit.Test;
+import org.junit.rules.ExpectedException;
 
 /**
  * @author Jan Koehnlein - Initial contribution and API
  */
 public class DeclarativeQualifiedNameConverterTest extends Assert {
+	@Rule
+	public ExpectedException thrown = ExpectedException.none();
 
 	@Test public void testQualifiedNameConverter() throws Exception {
 		IQualifiedNameConverter qualifiedNameConverter = new IQualifiedNameConverter.DefaultImpl() {
@@ -25,13 +29,50 @@ public class DeclarativeQualifiedNameConverterTest extends Assert {
 		QualifiedName qn = QualifiedName.create("foo", "bar", "baz");
 		assertEquals("foo!bar!baz", qualifiedNameConverter.toString(qn));
 		assertEquals(qn, qualifiedNameConverter.toQualifiedName("foo!bar!baz"));
-		try {
-			qualifiedNameConverter.toQualifiedName(null);
-			fail("Exception expected");
-		} catch(IllegalArgumentException e) {}
-		try {
-			qualifiedNameConverter.toQualifiedName("");
-			fail("Exception expected");
-		} catch(IllegalArgumentException e) {}
+	
+		
+		qualifiedNameConverter = new IQualifiedNameConverter.DefaultImpl() {
+			@Override
+			public String getDelimiter() {
+				return " ";
+			}
+		};
+		assertEquals("foo bar baz", qualifiedNameConverter.toString(qn));
+		assertEquals(qn, qualifiedNameConverter.toQualifiedName("foo bar baz"));
+		
+		thrown.expect(IllegalArgumentException.class);
+		thrown.expectMessage("Qualified name cannot be null");
+		qualifiedNameConverter.toQualifiedName(null);
+		
+		thrown.expect(IllegalArgumentException.class);
+		thrown.expectMessage("Qualified name cannot be empty");
+		qualifiedNameConverter.toQualifiedName("");
 	}
+
+	@Test public void testQualifiedNameConverter_emptyDelimiter() throws Exception {
+		IQualifiedNameConverter qualifiedNameConverter = new IQualifiedNameConverter.DefaultImpl() {
+			@Override
+			public String getDelimiter() {
+				return "";
+			}
+		};
+
+		QualifiedName qn = QualifiedName.create("foo", "bar", "baz");
+		assertEquals("foobarbaz", qualifiedNameConverter.toString(qn));
+		assertEquals(QualifiedName.create("foobarbaz"), qualifiedNameConverter.toQualifiedName("foobarbaz"));
+	}
+
+	@Test public void testQualifiedNameConverter_nullDelimiter() throws Exception {
+		IQualifiedNameConverter qualifiedNameConverter = new IQualifiedNameConverter.DefaultImpl() {
+			@Override
+			public String getDelimiter() {
+				return null;
+			}
+		};
+		QualifiedName qn = QualifiedName.create("foo", "bar", "baz");
+		assertEquals("foonullbarnullbaz", qualifiedNameConverter.toString(qn));
+		assertEquals(QualifiedName.create("foobarbaz"), qualifiedNameConverter.toQualifiedName("foobarbaz"));
+		
+	}
+
 }
diff --git a/org.eclipse.xtext/src/org/eclipse/xtext/naming/IQualifiedNameConverter.java b/org.eclipse.xtext/src/org/eclipse/xtext/naming/IQualifiedNameConverter.java
index 0d8070c81..c6dac7220 100644
--- a/org.eclipse.xtext/src/org/eclipse/xtext/naming/IQualifiedNameConverter.java
+++ b/org.eclipse.xtext/src/org/eclipse/xtext/naming/IQualifiedNameConverter.java
@@ -11,6 +11,7 @@ import java.util.List;
 
 import org.eclipse.xtext.util.Strings;
 
+import com.google.common.base.Preconditions;
 import com.google.inject.ImplementedBy;
 import com.google.inject.Singleton;
 
@@ -53,15 +54,14 @@ public interface IQualifiedNameConverter {
 		 */
 		@Override
 		public QualifiedName toQualifiedName(String qualifiedNameAsString) {
-			if (qualifiedNameAsString == null)
-				throw new IllegalArgumentException("Qualified name cannot be null");
-			if (qualifiedNameAsString.equals(""))
-				throw new IllegalArgumentException("Qualified name cannot be empty");
-			if (Strings.isEmpty(getDelimiter()))
+			Preconditions.checkArgument(qualifiedNameAsString != null, "Qualified name cannot be null");
+			Preconditions.checkArgument(!qualifiedNameAsString.isEmpty(), "Qualified name cannot be empty");
+			String delimiter = getDelimiter();
+			if (Strings.isEmpty(delimiter))
 				return QualifiedName.create(qualifiedNameAsString);
-			List<String> segs = getDelimiter().length() == 1
-					? Strings.split(qualifiedNameAsString, getDelimiter().charAt(0))
-					: Strings.split(qualifiedNameAsString, getDelimiter());
+			List<String> segs = delimiter.length() == 1
+					? Strings.split(qualifiedNameAsString, delimiter.charAt(0))
+					: Strings.split(qualifiedNameAsString, delimiter);
 			return QualifiedName.create(segs);
 		}