diff --git a/org.eclipse.xtext.xtext.generator/src/org/eclipse/xtext/xtext/generator/CodeConfig.xtend b/org.eclipse.xtext.xtext.generator/src/org/eclipse/xtext/xtext/generator/CodeConfig.xtend
index e178f944e..4be1f8b49 100644
--- a/org.eclipse.xtext.xtext.generator/src/org/eclipse/xtext/xtext/generator/CodeConfig.xtend
+++ b/org.eclipse.xtext.xtext.generator/src/org/eclipse/xtext/xtext/generator/CodeConfig.xtend
@@ -8,6 +8,7 @@
 package org.eclipse.xtext.xtext.generator
 
 import com.google.inject.Injector
+import java.nio.charset.Charset
 import java.text.SimpleDateFormat
 import java.util.Date
 import java.util.List
@@ -15,7 +16,6 @@ import org.eclipse.xtend.lib.annotations.Accessors
 import org.eclipse.xtext.util.Strings
 import org.eclipse.xtext.util.XtextVersion
 import org.eclipse.xtext.xtext.generator.model.annotations.IClassAnnotation
-import java.nio.charset.Charset
 
 /**
  * Configuration object for generated code.
diff --git a/org.eclipse.xtext.xtext.generator/src/org/eclipse/xtext/xtext/generator/model/GeneratedJavaFileAccess.xtend b/org.eclipse.xtext.xtext.generator/src/org/eclipse/xtext/xtext/generator/model/GeneratedJavaFileAccess.xtend
index 4c3f096fc..f2df3e634 100644
--- a/org.eclipse.xtext.xtext.generator/src/org/eclipse/xtext/xtext/generator/model/GeneratedJavaFileAccess.xtend
+++ b/org.eclipse.xtext.xtext.generator/src/org/eclipse/xtext/xtext/generator/model/GeneratedJavaFileAccess.xtend
@@ -4,7 +4,6 @@ import java.util.List
 import org.eclipse.xtend.lib.annotations.Accessors
 import org.eclipse.xtend2.lib.StringConcatenationClient
 import org.eclipse.xtext.xtext.generator.CodeConfig
-import org.eclipse.xtext.xtext.generator.model.JavaFileAccess.JavaTypeAwareStringConcatenation
 import org.eclipse.xtext.xtext.generator.model.annotations.IClassAnnotation
 
 /**
@@ -49,7 +48,7 @@ class GeneratedJavaFileAccess extends JavaFileAccess {
 	}
 	
 	private def getClassAnnotations() {
-		annotations + codeConfig.classAnnotations.filter[appliesTo(this)]
+		(annotations + codeConfig.classAnnotations.filter[appliesTo(this)]).toSet
 	}
 	
 	override getInternalContent() '''
diff --git a/org.eclipse.xtext.xtext.generator/src/org/eclipse/xtext/xtext/generator/model/annotations/GeneratedClassAnnotation.xtend b/org.eclipse.xtext.xtext.generator/src/org/eclipse/xtext/xtext/generator/model/annotations/GeneratedClassAnnotation.xtend
index e9e5f8c25..05fba1630 100644
--- a/org.eclipse.xtext.xtext.generator/src/org/eclipse/xtext/xtext/generator/model/annotations/GeneratedClassAnnotation.xtend
+++ b/org.eclipse.xtext.xtext.generator/src/org/eclipse/xtext/xtext/generator/model/annotations/GeneratedClassAnnotation.xtend
@@ -69,5 +69,13 @@ class GeneratedClassAnnotation implements IClassAnnotation {
 	override toString() {
 		generate.toString
 	}
+	
+	override equals(Object obj) {
+		return obj instanceof GeneratedClassAnnotation
+	}
+	
+	override hashCode() {
+		return class.name.hashCode;
+	}
 
 }
diff --git a/org.eclipse.xtext.xtext.generator/src/org/eclipse/xtext/xtext/generator/model/annotations/IClassAnnotation.xtend b/org.eclipse.xtext.xtext.generator/src/org/eclipse/xtext/xtext/generator/model/annotations/IClassAnnotation.xtend
index d088092f3..637633b6b 100644
--- a/org.eclipse.xtext.xtext.generator/src/org/eclipse/xtext/xtext/generator/model/annotations/IClassAnnotation.xtend
+++ b/org.eclipse.xtext.xtext.generator/src/org/eclipse/xtext/xtext/generator/model/annotations/IClassAnnotation.xtend
@@ -7,6 +7,7 @@
  *******************************************************************************/
 package org.eclipse.xtext.xtext.generator.model.annotations
 
+import java.lang.annotation.Repeatable
 import org.eclipse.xtext.xtext.generator.XtextGenerator
 import org.eclipse.xtext.xtext.generator.model.JavaFileAccess
 import org.eclipse.xtext.xtext.generator.model.TypeReference
@@ -14,6 +15,12 @@ import org.eclipse.xtext.xtext.generator.model.TypeReference
 /** 
  * Class annotations can be added to the {@link XtextGenerator} workflow component in order
  * to configure specific Java annotations to be added to each generated class.
+ * <br/><br/>
+ * Make sure that you implement {@link Object#equals(Object)} and {@link Object#hashCode()} to fulfill following contract
+ * <ul>
+ * 	<li>If the underlying Annotation is {@link Repeatable} then the methods should behave like in {@link Object}.</li>
+ * 	<li>If the underlying Annotation is NOT {@link Repeatable} then {@link Object#equals(Object)} should return true for all instances and {@link Object#hashCode()} should return the same value for all instances</li>
+ * </ul>
  */
 interface IClassAnnotation {
 	
diff --git a/org.eclipse.xtext.xtext.generator/src/org/eclipse/xtext/xtext/generator/model/annotations/SingletonClassAnnotation.xtend b/org.eclipse.xtext.xtext.generator/src/org/eclipse/xtext/xtext/generator/model/annotations/SingletonClassAnnotation.xtend
index 9f05c3b3b..72a274f33 100644
--- a/org.eclipse.xtext.xtext.generator/src/org/eclipse/xtext/xtext/generator/model/annotations/SingletonClassAnnotation.xtend
+++ b/org.eclipse.xtext.xtext.generator/src/org/eclipse/xtext/xtext/generator/model/annotations/SingletonClassAnnotation.xtend
@@ -31,4 +31,12 @@ class SingletonClassAnnotation implements IClassAnnotation {
 	override toString() {
 		generate.toString
 	}
+	
+	override equals(Object obj) {
+		return obj instanceof SingletonClassAnnotation
+	}
+	
+	override hashCode() {
+		return class.name.hashCode;
+	}
 }
diff --git a/org.eclipse.xtext.xtext.generator/src/org/eclipse/xtext/xtext/generator/model/annotations/SuppressWarningsAnnotation.xtend b/org.eclipse.xtext.xtext.generator/src/org/eclipse/xtext/xtext/generator/model/annotations/SuppressWarningsAnnotation.xtend
index d574da782..28c8a4629 100644
--- a/org.eclipse.xtext.xtext.generator/src/org/eclipse/xtext/xtext/generator/model/annotations/SuppressWarningsAnnotation.xtend
+++ b/org.eclipse.xtext.xtext.generator/src/org/eclipse/xtext/xtext/generator/model/annotations/SuppressWarningsAnnotation.xtend
@@ -41,5 +41,14 @@ class SuppressWarningsAnnotation implements IClassAnnotation {
 
 	override toString() {
 		generate.toString
-	}	
+	}
+	
+	override equals(Object obj) {
+		return obj instanceof SuppressWarningsAnnotation
+	}
+	
+	override hashCode() {
+		return class.name.hashCode;
+	}
+	
 }
diff --git a/org.eclipse.xtext.xtext.generator/xtend-gen/org/eclipse/xtext/xtext/generator/model/GeneratedJavaFileAccess.java b/org.eclipse.xtext.xtext.generator/xtend-gen/org/eclipse/xtext/xtext/generator/model/GeneratedJavaFileAccess.java
index 82f2abe62..7bb1c1a67 100644
--- a/org.eclipse.xtext.xtext.generator/xtend-gen/org/eclipse/xtext/xtext/generator/model/GeneratedJavaFileAccess.java
+++ b/org.eclipse.xtext.xtext.generator/xtend-gen/org/eclipse/xtext/xtext/generator/model/GeneratedJavaFileAccess.java
@@ -2,6 +2,7 @@ package org.eclipse.xtext.xtext.generator.model;
 
 import com.google.common.collect.Iterables;
 import java.util.List;
+import java.util.Set;
 import java.util.function.Consumer;
 import org.eclipse.xtend.lib.annotations.Accessors;
 import org.eclipse.xtend2.lib.StringConcatenation;
@@ -65,12 +66,12 @@ public class GeneratedJavaFileAccess extends JavaFileAccess {
     return _xblockexpression;
   }
   
-  private Iterable<IClassAnnotation> getClassAnnotations() {
+  private Set<IClassAnnotation> getClassAnnotations() {
     final Function1<IClassAnnotation, Boolean> _function = (IClassAnnotation it) -> {
       return Boolean.valueOf(it.appliesTo(this));
     };
     Iterable<IClassAnnotation> _filter = IterableExtensions.<IClassAnnotation>filter(this.codeConfig.getClassAnnotations(), _function);
-    return Iterables.<IClassAnnotation>concat(this.annotations, _filter);
+    return IterableExtensions.<IClassAnnotation>toSet(Iterables.<IClassAnnotation>concat(this.annotations, _filter));
   }
   
   @Override
@@ -79,7 +80,7 @@ public class GeneratedJavaFileAccess extends JavaFileAccess {
     _builder.append(this.typeComment);
     _builder.newLineIfNotEmpty();
     {
-      Iterable<IClassAnnotation> _classAnnotations = this.getClassAnnotations();
+      Set<IClassAnnotation> _classAnnotations = this.getClassAnnotations();
       for(final IClassAnnotation annot : _classAnnotations) {
         CharSequence _generate = annot.generate();
         _builder.append(_generate);
diff --git a/org.eclipse.xtext.xtext.generator/xtend-gen/org/eclipse/xtext/xtext/generator/model/annotations/GeneratedClassAnnotation.java b/org.eclipse.xtext.xtext.generator/xtend-gen/org/eclipse/xtext/xtext/generator/model/annotations/GeneratedClassAnnotation.java
index 772360a26..5641fe081 100644
--- a/org.eclipse.xtext.xtext.generator/xtend-gen/org/eclipse/xtext/xtext/generator/model/annotations/GeneratedClassAnnotation.java
+++ b/org.eclipse.xtext.xtext.generator/xtend-gen/org/eclipse/xtext/xtext/generator/model/annotations/GeneratedClassAnnotation.java
@@ -80,6 +80,16 @@ public class GeneratedClassAnnotation implements IClassAnnotation {
     return this.generate().toString();
   }
   
+  @Override
+  public boolean equals(final Object obj) {
+    return (obj instanceof GeneratedClassAnnotation);
+  }
+  
+  @Override
+  public int hashCode() {
+    return this.getClass().getName().hashCode();
+  }
+  
   @Pure
   public boolean isIncludeDate() {
     return this.includeDate;
diff --git a/org.eclipse.xtext.xtext.generator/xtend-gen/org/eclipse/xtext/xtext/generator/model/annotations/IClassAnnotation.java b/org.eclipse.xtext.xtext.generator/xtend-gen/org/eclipse/xtext/xtext/generator/model/annotations/IClassAnnotation.java
index 02160a9df..485f0f8ef 100644
--- a/org.eclipse.xtext.xtext.generator/xtend-gen/org/eclipse/xtext/xtext/generator/model/annotations/IClassAnnotation.java
+++ b/org.eclipse.xtext.xtext.generator/xtend-gen/org/eclipse/xtext/xtext/generator/model/annotations/IClassAnnotation.java
@@ -7,6 +7,7 @@
  */
 package org.eclipse.xtext.xtext.generator.model.annotations;
 
+import java.lang.annotation.Repeatable;
 import org.eclipse.xtext.xtext.generator.XtextGenerator;
 import org.eclipse.xtext.xtext.generator.model.JavaFileAccess;
 import org.eclipse.xtext.xtext.generator.model.TypeReference;
@@ -14,6 +15,12 @@ import org.eclipse.xtext.xtext.generator.model.TypeReference;
 /**
  * Class annotations can be added to the {@link XtextGenerator} workflow component in order
  * to configure specific Java annotations to be added to each generated class.
+ * <br/><br/>
+ * Make sure that you implement {@link Object#equals(Object)} and {@link Object#hashCode()} to fulfill following contract
+ * <ul>
+ * 	<li>If the underlying Annotation is {@link Repeatable} then the methods should behave like in {@link Object}.</li>
+ * 	<li>If the underlying Annotation is NOT {@link Repeatable} then {@link Object#equals(Object)} should return true for all instances and {@link Object#hashCode()} should return the same value for all instances</li>
+ * </ul>
  */
 @SuppressWarnings("all")
 public interface IClassAnnotation {
diff --git a/org.eclipse.xtext.xtext.generator/xtend-gen/org/eclipse/xtext/xtext/generator/model/annotations/SingletonClassAnnotation.java b/org.eclipse.xtext.xtext.generator/xtend-gen/org/eclipse/xtext/xtext/generator/model/annotations/SingletonClassAnnotation.java
index 5428b90d2..f01adb3c1 100644
--- a/org.eclipse.xtext.xtext.generator/xtend-gen/org/eclipse/xtext/xtext/generator/model/annotations/SingletonClassAnnotation.java
+++ b/org.eclipse.xtext.xtext.generator/xtend-gen/org/eclipse/xtext/xtext/generator/model/annotations/SingletonClassAnnotation.java
@@ -36,4 +36,14 @@ public class SingletonClassAnnotation implements IClassAnnotation {
   public String toString() {
     return this.generate().toString();
   }
+  
+  @Override
+  public boolean equals(final Object obj) {
+    return (obj instanceof SingletonClassAnnotation);
+  }
+  
+  @Override
+  public int hashCode() {
+    return this.getClass().getName().hashCode();
+  }
 }
diff --git a/org.eclipse.xtext.xtext.generator/xtend-gen/org/eclipse/xtext/xtext/generator/model/annotations/SuppressWarningsAnnotation.java b/org.eclipse.xtext.xtext.generator/xtend-gen/org/eclipse/xtext/xtext/generator/model/annotations/SuppressWarningsAnnotation.java
index e176500ab..b5bcd7407 100644
--- a/org.eclipse.xtext.xtext.generator/xtend-gen/org/eclipse/xtext/xtext/generator/model/annotations/SuppressWarningsAnnotation.java
+++ b/org.eclipse.xtext.xtext.generator/xtend-gen/org/eclipse/xtext/xtext/generator/model/annotations/SuppressWarningsAnnotation.java
@@ -61,6 +61,16 @@ public class SuppressWarningsAnnotation implements IClassAnnotation {
     return this.generate().toString();
   }
   
+  @Override
+  public boolean equals(final Object obj) {
+    return (obj instanceof SuppressWarningsAnnotation);
+  }
+  
+  @Override
+  public int hashCode() {
+    return this.getClass().getName().hashCode();
+  }
+  
   @Pure
   public String getSuppress() {
     return this.suppress;