Upgraded to Xtext 2.2.1.
diff --git a/com.google.eclipse.protobuf.feature/feature.xml b/com.google.eclipse.protobuf.feature/feature.xml
index 6a6e436..b84e30b 100644
--- a/com.google.eclipse.protobuf.feature/feature.xml
+++ b/com.google.eclipse.protobuf.feature/feature.xml
@@ -39,7 +39,7 @@
       <import plugin="org.eclipse.emf.databinding"/>
       <import plugin="org.eclipse.core.resources"/>
       <import plugin="org.eclipse.core.filesystem" version="1.3.100" match="greaterOrEqual"/>
-      <import plugin="org.eclipse.xtext" version="2.1.1" match="greaterOrEqual"/>
+      <import plugin="org.eclipse.xtext" version="2.2.1" match="greaterOrEqual"/>
       <import plugin="org.eclipse.compare.core" version="3.5.200" match="greaterOrEqual"/>
       <import plugin="org.eclipse.ui.workbench.texteditor"/>
    </requires>