diff --git a/plugins/org.eclipse.xtext/src/org/eclipse/xtext/naming/IQualifiedNameConverter.java b/plugins/org.eclipse.xtext/src/org/eclipse/xtext/naming/IQualifiedNameConverter.java
index e5a77cc00..9b45fe6cc 100644
--- a/plugins/org.eclipse.xtext/src/org/eclipse/xtext/naming/IQualifiedNameConverter.java
+++ b/plugins/org.eclipse.xtext/src/org/eclipse/xtext/naming/IQualifiedNameConverter.java
@@ -12,6 +12,7 @@ import java.util.List;
 import org.eclipse.xtext.util.Strings;
 
 import com.google.inject.ImplementedBy;
+import com.google.inject.Singleton;
 
 /**
  * Converts {@link QualifiedName}s to strings and back.
@@ -28,6 +29,7 @@ public interface IQualifiedNameConverter {
 
 	QualifiedName toQualifiedName(String qualifiedNameAsText);
 
+	@Singleton
 	static class DefaultImpl implements IQualifiedNameConverter {
 
 		/**
diff --git a/plugins/org.eclipse.xtext/src/org/eclipse/xtext/resource/DerivedStateAwareResourceDescriptionManager.java b/plugins/org.eclipse.xtext/src/org/eclipse/xtext/resource/DerivedStateAwareResourceDescriptionManager.java
index 0ef559c3e..2b1c58189 100644
--- a/plugins/org.eclipse.xtext/src/org/eclipse/xtext/resource/DerivedStateAwareResourceDescriptionManager.java
+++ b/plugins/org.eclipse.xtext/src/org/eclipse/xtext/resource/DerivedStateAwareResourceDescriptionManager.java
@@ -18,6 +18,7 @@ import org.eclipse.xtext.util.IResourceScopeCache;
 import org.eclipse.xtext.util.RuntimeIOException;
 
 import com.google.inject.Inject;
+import com.google.inject.Singleton;
 
 /**
  * 
@@ -26,6 +27,7 @@ import com.google.inject.Inject;
  * @author Sven Efftinge - Initial contribution and API
  * @since 2.1
  */
+@Singleton
 public class DerivedStateAwareResourceDescriptionManager extends DefaultResourceDescriptionManager {
 	
 	private final static Logger log = Logger.getLogger(DerivedStateAwareResourceDescriptionManager.class);
diff --git a/plugins/org.eclipse.xtext/src/org/eclipse/xtext/resource/impl/DefaultResourceDescriptionStrategy.java b/plugins/org.eclipse.xtext/src/org/eclipse/xtext/resource/impl/DefaultResourceDescriptionStrategy.java
index 5c38b3da4..2b3375401 100644
--- a/plugins/org.eclipse.xtext/src/org/eclipse/xtext/resource/impl/DefaultResourceDescriptionStrategy.java
+++ b/plugins/org.eclipse.xtext/src/org/eclipse/xtext/resource/impl/DefaultResourceDescriptionStrategy.java
@@ -25,12 +25,14 @@ import org.eclipse.xtext.resource.IReferenceDescription;
 import org.eclipse.xtext.util.IAcceptor;
 
 import com.google.inject.Inject;
+import com.google.inject.Singleton;
 
 /**
  * By default, all elements with a not null <code>name</code> feature and all cross-resource crossrefs are indexed.
  * 
  * @author Jan Koehnlein - Initial contribution and API
  */
+@Singleton
 public class DefaultResourceDescriptionStrategy implements IDefaultResourceDescriptionStrategy {
 
 	private final static Logger LOG = Logger.getLogger(DefaultResourceDescriptionStrategy.class);