diff --git a/idea/src/org/jetbrains/jet/codegen/ExpressionCodegen.java b/idea/src/org/jetbrains/jet/codegen/ExpressionCodegen.java
index 2f05123db48..2930cd49f68 100644
--- a/idea/src/org/jetbrains/jet/codegen/ExpressionCodegen.java
+++ b/idea/src/org/jetbrains/jet/codegen/ExpressionCodegen.java
@@ -3,10 +3,7 @@ package org.jetbrains.jet.codegen;
 import com.intellij.psi.*;
 import org.jetbrains.jet.lang.psi.*;
 import org.jetbrains.jet.lang.resolve.BindingContext;
-import org.jetbrains.jet.lang.types.DeclarationDescriptor;
-import org.jetbrains.jet.lang.types.FunctionDescriptor;
-import org.jetbrains.jet.lang.types.JetStandardClasses;
-import org.jetbrains.jet.lang.types.JetType;
+import org.jetbrains.jet.lang.types.*;
 import org.objectweb.asm.Label;
 import org.objectweb.asm.MethodVisitor;
 import org.objectweb.asm.Opcodes;
@@ -24,10 +21,12 @@ public class ExpressionCodegen extends JetVisitor {
     private final Stack<Label> myLoopEnds = new Stack<Label>();
 
     private final InstructionAdapter v;
+    private final JetStandardLibrary stdlib;
     private final FrameMap myMap;
     private final BindingContext bindingContext;
 
-    public ExpressionCodegen(MethodVisitor v, BindingContext bindingContext, FrameMap myMap) {
+    public ExpressionCodegen(MethodVisitor v, BindingContext bindingContext, JetStandardLibrary stdlib, FrameMap myMap) {
+        this.stdlib = stdlib;
         this.myMap = myMap;
         this.v = new InstructionAdapter(v);
         this.bindingContext = bindingContext;
@@ -333,6 +332,17 @@ public class ExpressionCodegen extends JetVisitor {
         }
     }
 
+    private void unbox(PsiType type) {
+        if (type instanceof PsiPrimitiveType) {
+            if (type == PsiType.INT) {
+                v.invokevirtual("java/lang/Integer", "intValue", "()I");
+            }
+            else {
+                throw new UnsupportedOperationException("Don't know how to unbox type " + type);
+            }
+        }
+    }
+
     private String getMethodDescriptor(PsiMethod method) {
         Type returnType = psiTypeToAsm(method.getReturnType());
         PsiParameter[] parameters = method.getParameterList().getParameters();
@@ -403,11 +413,28 @@ public class ExpressionCodegen extends JetVisitor {
         v.mark(end);
     }
 
-    /*
-        @Override
-        public void visitBinaryExpression(JetBinaryExpression expression) {
+    @Override
+    public void visitBinaryExpression(JetBinaryExpression expression) {
+        DeclarationDescriptor op = bindingContext.resolveReferenceExpression(expression.getOperationReference());
+        if (op instanceof FunctionDescriptor) {
+            DeclarationDescriptor cls = op.getContainingDeclaration();
+            if (cls instanceof ClassDescriptor && cls.getName().equals("Int")) {
+                if (op.getName().equals("plus")) {
+                    JetType returnType = ((FunctionDescriptor) op).getUnsubstitutedReturnType();
+                    if (returnType.equals(stdlib.getIntType())) {
+                        gen(expression.getLeft());
+                        unbox(PsiType.INT);
+                        gen(expression.getRight());
+                        unbox(PsiType.INT);
+                        v.add(Type.INT_TYPE);
+                        boxIfNeeded(PsiType.INT);
+                        return;
+                    }
+                }
+            }
         }
-    */
+        throw new UnsupportedOperationException("Don't know how to generate binary op " + expression);
+    }
 
     private Type getType(JetProperty var) {
         return InstructionAdapter.OBJECT_TYPE;  // TODO:
diff --git a/idea/src/org/jetbrains/jet/codegen/FunctionCodegen.java b/idea/src/org/jetbrains/jet/codegen/FunctionCodegen.java
index a7168b9d20f..833f89298ab 100644
--- a/idea/src/org/jetbrains/jet/codegen/FunctionCodegen.java
+++ b/idea/src/org/jetbrains/jet/codegen/FunctionCodegen.java
@@ -56,7 +56,7 @@ public class FunctionCodegen {
             frameMap.enter(parameter);
         }
 
-        bodyExpression.accept(new ExpressionCodegen(mv, bindingContext, frameMap));
+        bodyExpression.accept(new ExpressionCodegen(mv, bindingContext, standardLibrary, frameMap));
         generateReturn(mv, bodyExpression);
         mv.visitMaxs(0, 0);
         mv.visitEnd();
diff --git a/idea/testData/codegen/plus.jet b/idea/testData/codegen/plus.jet
new file mode 100644
index 00000000000..942e59d057b
--- /dev/null
+++ b/idea/testData/codegen/plus.jet
@@ -0,0 +1 @@
+fun f(a: Int, b: Int): Int { return a + b }
\ No newline at end of file
diff --git a/idea/tests/org/jetbrains/jet/codegen/ExpressionGenTest.java b/idea/tests/org/jetbrains/jet/codegen/ExpressionGenTest.java
index 2696c92edbe..08f44a730ba 100644
--- a/idea/tests/org/jetbrains/jet/codegen/ExpressionGenTest.java
+++ b/idea/tests/org/jetbrains/jet/codegen/ExpressionGenTest.java
@@ -60,7 +60,7 @@ public class ExpressionGenTest extends LightDaemonAnalyzerTestCase {
         JetProperty p = PsiTreeUtil.getParentOfType(getFile().findElementAt(0), JetProperty.class);
 
         TraceMethodVisitor trace = new TraceMethodVisitor();
-        p.getInitializer().accept(new ExpressionCodegen(trace, null, new FrameMap()));
+        p.getInitializer().accept(new ExpressionCodegen(trace, null, null, new FrameMap()));
 
         StringWriter out = new StringWriter();
         trace.print(new PrintWriter(out));
diff --git a/idea/tests/org/jetbrains/jet/codegen/NamespaceGenTest.java b/idea/tests/org/jetbrains/jet/codegen/NamespaceGenTest.java
index 4db4c157451..ccd078b485a 100644
--- a/idea/tests/org/jetbrains/jet/codegen/NamespaceGenTest.java
+++ b/idea/tests/org/jetbrains/jet/codegen/NamespaceGenTest.java
@@ -96,11 +96,21 @@ public class NamespaceGenTest extends LightCodeInsightFixtureTestCase {
     public void testHelloWorld() throws Exception {
         loadFile("helloWorld.jet");
 
-        final String text = generateToText();
-        System.out.println(text);
+        System.out.println(generateToText());
+
+        final Class aClass = generateToClass();
+        final Method main = firstMethod(aClass);   // assert that it can be verified
+    }
+
+    public void testPlus() throws Exception {
+        loadFile("plus.jet");
+
+        System.out.println(generateToText());
 
         final Class aClass = generateToClass();
         final Method main = firstMethod(aClass);
+        final int returnValue = (Integer) main.invoke(null, 37, 5);
+        assertEquals(42, returnValue);
     }
 
     private void loadFile(final String name) {
@@ -115,6 +125,7 @@ public class NamespaceGenTest extends LightCodeInsightFixtureTestCase {
                 new TraceClassVisitor(new PrintWriter(writer)),
                 namespace.getFQName());
         codegen.generate(namespace);
+        codegen.done();
         return writer.toString();
     }