diff --git a/de.darmstadt.tu.crossing.CrySL/src/de/darmstadt/tu/crossing/validation/CrySLValidator.java b/de.darmstadt.tu.crossing.CrySL/src/de/darmstadt/tu/crossing/validation/CrySLValidator.java
index 73162472..fb686160 100644
--- a/de.darmstadt.tu.crossing.CrySL/src/de/darmstadt/tu/crossing/validation/CrySLValidator.java
+++ b/de.darmstadt.tu.crossing.CrySL/src/de/darmstadt/tu/crossing/validation/CrySLValidator.java
@@ -6,7 +6,11 @@
 import org.eclipse.emf.ecore.EStructuralFeature;
 import org.eclipse.xtext.validation.Check;
 
+import de.darmstadt.tu.crossing.crySL.Event;
 import de.darmstadt.tu.crossing.crySL.ForbMethod;
+import de.darmstadt.tu.crossing.crySL.RequiredBlock;
+import de.darmstadt.tu.crossing.crySL.SuperType;
+import de.darmstadt.tu.crossing.crySL.impl.ObjectImpl;
 
 /**
  * This class contains custom validation rules. 
@@ -19,8 +23,32 @@ public class CrySLValidator extends AbstractCrySLValidator {
 
 	@Check
 	public void checkGreetingStartsWithCapital(ForbMethod greeting) {
-
+		
 	}
 	
-	
-}
+	/**
+	 * Add error markers for duplicate event labels.
+	 * 
+	 * @param s of type supertype being checked for duplicity 
+	 */
+	@Check
+	public void checkDuplicateEventLabel(SuperType s) {
+		
+		if(!(s instanceof ObjectImpl)) {
+			for(Event e : ((RequiredBlock) s.eContainer()).getReq_event()) {
+				for(Event ev : ((RequiredBlock) s.eContainer()).getReq_event()) {
+					if(e instanceof SuperType && ev instanceof SuperType) {
+						SuperType es = (SuperType) e;
+						SuperType evs = (SuperType) ev;
+						if(es != evs && es.getName().equals(evs.getName())) {
+							if(s.getName().contentEquals(es.getName()) 
+									&& s.getName().contentEquals(evs.getName())) {
+								error("Duplicate label", INVALID_NAME);
+							}
+						}
+					}
+				}
+			}
+		}
+	}
+}
\ No newline at end of file