diff --git a/idea/src/org/jetbrains/jet/codegen/ExpressionCodegen.java b/idea/src/org/jetbrains/jet/codegen/ExpressionCodegen.java
index e70430f1aa0..958e027e8f2 100644
--- a/idea/src/org/jetbrains/jet/codegen/ExpressionCodegen.java
+++ b/idea/src/org/jetbrains/jet/codegen/ExpressionCodegen.java
@@ -1288,9 +1288,20 @@ public class ExpressionCodegen extends JetVisitor {
                 intrinsic.generate(this, v, Type.VOID_TYPE, expression, Arrays.asList(lhs, expression.getRight()), false);
             }
             else {
-                throw new UnsupportedOperationException("TODO");
+                CallableMethod method = (CallableMethod) callable;
+                FunctionDescriptor fd = (FunctionDescriptor) op;
+                StackValue value = generateIntermediateValue(lhs);
+                final boolean keepReturnValue = !fd.getReturnType().equals(JetStandardClasses.getUnitType());
+                if (keepReturnValue) {
+                    value.dupReceiver(v, 0);
+                }
+                value.put(lhsType, v);
+                genToJVMStack(expression.getRight());
+                method.invoke(v);
+                if (keepReturnValue) {
+                    value.store(v);
+                }
             }
-
         }
     }
 
diff --git a/idea/testData/codegen/classes/overloadPlusAssign.jet b/idea/testData/codegen/classes/overloadPlusAssign.jet
new file mode 100644
index 00000000000..21459ecff1e
--- /dev/null
+++ b/idea/testData/codegen/classes/overloadPlusAssign.jet
@@ -0,0 +1,26 @@
+import java.util.*
+
+class ArrayWrapper<T>() {
+    val contents = ArrayList<T>()
+
+    fun add(item: T) {
+        contents.add(item)
+    }
+
+    fun plusAssign(rhs: ArrayWrapper<T>) {
+        contents.addAll(rhs.contents)
+    }
+
+    fun get(index: Int): T {
+        return contents.get(index)
+    }
+}
+
+fun box(): String {
+    val v1 = ArrayWrapper<String>()
+    val v2 = ArrayWrapper<String>()
+    v1.add("foo")
+    v2.add("bar")
+    v1 += v2
+    return if (v1.contents.size() == 2) "OK" else "fail"
+}
diff --git a/idea/testData/codegen/classes/overloadPlusAssignReturn.jet b/idea/testData/codegen/classes/overloadPlusAssignReturn.jet
new file mode 100644
index 00000000000..28fb9af2652
--- /dev/null
+++ b/idea/testData/codegen/classes/overloadPlusAssignReturn.jet
@@ -0,0 +1,30 @@
+import java.util.*
+
+class ArrayWrapper<T>() {
+    val contents = ArrayList<T>()
+
+    fun add(item: T) {
+        contents.add(item)
+    }
+
+    fun plusAssign(rhs: ArrayWrapper<T>): ArrayWrapper<T> {
+        val result = ArrayWrapper<T>()
+        result.contents.addAll(contents)
+        result.contents.addAll(rhs.contents)
+        return result
+    }
+
+    fun get(index: Int): T {
+        return contents.get(index)
+    }
+}
+
+fun box(): String {
+    val v1 = ArrayWrapper<String>()
+    val v2 = ArrayWrapper<String>()
+    v1.add("foo")
+    val v3 = v1
+    v2.add("bar")
+    v1 += v2
+    return if (v1.contents.size() == 2 && v3.contents.size() == 1) "OK" else "fail"
+}
diff --git a/idea/tests/org/jetbrains/jet/codegen/ClassGenTest.java b/idea/tests/org/jetbrains/jet/codegen/ClassGenTest.java
index aefcec68fab..aac3d2ceb7a 100644
--- a/idea/tests/org/jetbrains/jet/codegen/ClassGenTest.java
+++ b/idea/tests/org/jetbrains/jet/codegen/ClassGenTest.java
@@ -140,6 +140,14 @@ public class ClassGenTest extends CodegenTestCase {
         blackBoxFile("classes/overloadUnaryOperator.jet");
     }
 
+    public void testOverloadPlusAssign() throws Exception {
+        blackBoxFile("classes/overloadPlusAssign.jet");
+    }
+
+    public void testOverloadPlusAssignReturn() throws Exception {
+        blackBoxFile("classes/overloadPlusAssignReturn.jet");
+    }
+
     public void testEnumClass() throws Exception {
         loadText("enum class Direction { NORTH; SOUTH; EAST; WEST }");
         final Class direction = loadAllClasses(generateClassesInFile()).get("Direction");