diff --git a/compiler/backend/src/org/jetbrains/jet/codegen/ImplementationBodyCodegen.java b/compiler/backend/src/org/jetbrains/jet/codegen/ImplementationBodyCodegen.java
index 780086f0389..567ad569bae 100644
--- a/compiler/backend/src/org/jetbrains/jet/codegen/ImplementationBodyCodegen.java
+++ b/compiler/backend/src/org/jetbrains/jet/codegen/ImplementationBodyCodegen.java
@@ -745,7 +745,7 @@ public class ImplementationBodyCodegen extends ClassBodyCodegen {
     }
 
     private void generateTraitMethods(ExpressionCodegen codegen) {
-        if (!(myClass instanceof JetClass) || ((JetClass)myClass).isTrait() || ((JetClass)myClass).hasModifier(JetTokens.ABSTRACT_KEYWORD))
+        if (myClass instanceof JetClass && (((JetClass)myClass).isTrait() || ((JetClass)myClass).hasModifier(JetTokens.ABSTRACT_KEYWORD)))
             return;
         
         for (Pair<CallableMemberDescriptor, CallableMemberDescriptor> needDelegates : getTraitImplementations(descriptor)) {
diff --git a/compiler/testData/codegen/regressions/kt2399.kt b/compiler/testData/codegen/regressions/kt2399.kt
new file mode 100644
index 00000000000..8f4de76c99e
--- /dev/null
+++ b/compiler/testData/codegen/regressions/kt2399.kt
@@ -0,0 +1,43 @@
+import java.util.Collection
+import java.util.ArrayList
+
+class JsonObject {
+}
+
+class JsonArray {
+}
+
+class ProjectInfo {
+    public fun toString(): String = "OK"
+}
+
+public trait Parser<in IN: Any, out OUT: Any> {
+    public fun parse(source: IN): OUT
+}
+
+public trait MultiParser<in IN: Any, out OUT: Any> {
+    public fun parse(source: IN): Collection<OUT>
+}
+
+public trait JsonParser<T: Any>: Parser<JsonObject, T>, MultiParser<JsonArray, T> {
+    public override fun parse(source: JsonArray): Collection<T> {
+        return ArrayList<T>()
+    }
+}
+
+public abstract class ProjectInfoJsonParser(): JsonParser<ProjectInfo> {
+    public override fun parse(source: JsonObject): ProjectInfo {
+        return ProjectInfo()
+    }
+}
+
+class ProjectApiContext {
+    public val projectInfoJsonParser: ProjectInfoJsonParser = object : ProjectInfoJsonParser(){
+    }
+}
+
+fun box(): String {
+    val context = ProjectApiContext()
+    val array = context.projectInfoJsonParser.parse(JsonArray())
+    return if (array != null) "OK" else "fail"
+}
diff --git a/compiler/tests/org/jetbrains/jet/codegen/TraitsTest.java b/compiler/tests/org/jetbrains/jet/codegen/TraitsTest.java
index 6cdb140549f..25e56a2e115 100644
--- a/compiler/tests/org/jetbrains/jet/codegen/TraitsTest.java
+++ b/compiler/tests/org/jetbrains/jet/codegen/TraitsTest.java
@@ -18,7 +18,7 @@ package org.jetbrains.jet.codegen;
 
 import org.jetbrains.jet.ConfigurationKind;
 
-public class TraitsTest  extends CodegenTestCase {
+public class TraitsTest extends CodegenTestCase {
 
     @Override
     protected void setUp() throws Exception {
@@ -31,29 +31,33 @@ public class TraitsTest  extends CodegenTestCase {
         return "traits";
     }
 
-    public void testSimple () throws Exception {
+    public void testSimple () {
         blackBoxFile("traits/simple.jet");
 //        System.out.println(generateToText());
     }
 
-    public void testWithRequired () throws Exception {
+    public void testWithRequired () {
         blackBoxFile("traits/withRequired.jet");
 //        System.out.println(generateToText());
     }
 
-    public void testMultiple () throws Exception {
+    public void testMultiple () {
         blackBoxFile("traits/multiple.jet");
     }
 
-    public void testStdlib () throws Exception {
+    public void testStdlib () {
         blackBoxFile("traits/stdlib.jet");
     }
 
-    public void testInheritedFun() throws Exception {
+    public void testInheritedFun() {
         blackBoxFile("traits/inheritedFun.jet");
     }
 
-    public void testInheritedVar() throws Exception {
+    public void testInheritedVar() {
         blackBoxFile("traits/inheritedVar.jet");
     }
+    
+    public void testKt2399() {
+        blackBoxFile("regressions/kt2399.kt");
+    }
 }