diff --git a/src/main/java/spoon/support/reflect/declaration/CtTypeImpl.java b/src/main/java/spoon/support/reflect/declaration/CtTypeImpl.java
index 1931c7b88f7..28b795b875b 100644
--- a/src/main/java/spoon/support/reflect/declaration/CtTypeImpl.java
+++ b/src/main/java/spoon/support/reflect/declaration/CtTypeImpl.java
@@ -16,18 +16,6 @@
  */
 package spoon.support.reflect.declaration;
 
-import static spoon.reflect.ModelElementContainerDefaultCapacities.TYPE_TYPE_PARAMETERS_CONTAINER_DEFAULT_CAPACITY;
-
-import java.lang.annotation.Annotation;
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.Collection;
-import java.util.Collections;
-import java.util.EnumSet;
-import java.util.HashSet;
-import java.util.List;
-import java.util.Set;
-
 import spoon.reflect.cu.CompilationUnit;
 import spoon.reflect.declaration.CtAnnotation;
 import spoon.reflect.declaration.CtAnnotationType;
@@ -59,6 +47,18 @@
 import spoon.support.util.QualifiedNameBasedSortedSet;
 import spoon.support.util.SignatureBasedSortedSet;
 
+import java.lang.annotation.Annotation;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.EnumSet;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+
+import static spoon.reflect.ModelElementContainerDefaultCapacities.TYPE_TYPE_PARAMETERS_CONTAINER_DEFAULT_CAPACITY;
+
 /**
  * The implementation for {@link spoon.reflect.declaration.CtType}.
  */
@@ -512,7 +512,7 @@ public boolean isAssignableFrom(CtTypeReference<?> type) {
 	@Override
 	public <M, C extends CtType<T>> C addMethod(CtMethod<M> method) {
 		if (method != null) {
-			for (CtTypeMember typeMember: typeMembers) {
+			for (CtTypeMember typeMember: new ArrayList<>(typeMembers)) {
 				if (!(typeMember instanceof CtMethod)) {
 					continue;
 				}
diff --git a/src/test/java/spoon/test/method/MethodTest.java b/src/test/java/spoon/test/method/MethodTest.java
index f04aa723ca2..283fb77e5a4 100644
--- a/src/test/java/spoon/test/method/MethodTest.java
+++ b/src/test/java/spoon/test/method/MethodTest.java
@@ -26,9 +26,15 @@
 import spoon.test.delete.testclasses.Adobada;
 import spoon.test.method.testclasses.Tacos;
 
+import java.util.ArrayList;
+import java.util.ConcurrentModificationException;
+import java.util.HashSet;
+
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.fail;
 import static spoon.testing.utils.ModelUtils.build;
 import static spoon.testing.utils.ModelUtils.buildClass;
+import static spoon.testing.utils.ModelUtils.createFactory;
 
 public class MethodTest {
 	@Test
@@ -53,4 +59,16 @@ public void testSearchMethodWithGeneric() throws Exception {
 		method1 = aTacos.getMethod("method1", aTacos.getFactory().Type().objectType());
 		assertEquals("public <T> void method1(T t) {" + System.lineSeparator() + "}", method1.toString());
 	}
+
+	@Test
+	public void testAddSameMethodsTwoTimes() throws Exception {
+		final Factory factory = createFactory();
+		final CtClass<Object> tacos = factory.Class().create("Tacos");
+		final CtMethod<Void> method = factory.Method().create(tacos, new HashSet<>(), factory.Type().voidType(), "m", new ArrayList<>(), new HashSet<>());
+		try {
+			tacos.addMethod(method.clone());
+		} catch (ConcurrentModificationException e) {
+			fail();
+		}
+	}
 }