diff --git a/html4j/src/main/java/org/teavm/html4j/JavaScriptConv.java b/html4j/src/main/java/org/teavm/html4j/JavaScriptConv.java
index 2c4f53846..8ef623d13 100644
--- a/html4j/src/main/java/org/teavm/html4j/JavaScriptConv.java
+++ b/html4j/src/main/java/org/teavm/html4j/JavaScriptConv.java
@@ -17,10 +17,6 @@ package org.teavm.html4j;
 
 import org.teavm.backend.javascript.spi.GeneratedBy;
 
-/**
- *
- * @author Alexey Andreev
- */
 public final class JavaScriptConv {
     private JavaScriptConv() {
     }
diff --git a/html4j/src/main/java/org/teavm/html4j/JavaScriptConvGenerator.java b/html4j/src/main/java/org/teavm/html4j/JavaScriptConvGenerator.java
index 500923af8..a415a1b0f 100644
--- a/html4j/src/main/java/org/teavm/html4j/JavaScriptConvGenerator.java
+++ b/html4j/src/main/java/org/teavm/html4j/JavaScriptConvGenerator.java
@@ -21,10 +21,6 @@ import org.teavm.backend.javascript.spi.Generator;
 import org.teavm.backend.javascript.spi.GeneratorContext;
 import org.teavm.model.*;
 
-/**
- *
- * @author Alexey Andreev
- */
 public class JavaScriptConvGenerator implements Generator {
     static final MethodReference intValueMethod = new MethodReference(Integer.class, "intValue", int.class);
     static final MethodReference booleanValueMethod = new MethodReference(Boolean.class, "booleanValue", boolean.class);
@@ -66,7 +62,7 @@ public class JavaScriptConvGenerator implements Generator {
     private void generateToJavaScript(GeneratorContext context, SourceWriter writer) throws IOException {
         String obj = context.getParameterName(1);
         writer.append("if (" + obj + " === null || " + obj + " === undefined) {").softNewLine().indent();
-        writer.append("return " + obj + ";").softNewLine();
+        writer.append("return null;").softNewLine();
 
         writer.outdent().append("} else if (typeof " + obj + " === 'number') {").indent().softNewLine();
         writer.append("return " + obj + ";").softNewLine();
@@ -118,7 +114,7 @@ public class JavaScriptConvGenerator implements Generator {
         String type = context.getParameterName(2);
         writer.append("if (" + obj + " === null || " + obj + " === undefined)").ws().append("{")
                 .softNewLine().indent();
-        writer.append("return " + obj + ";").softNewLine();
+        writer.append("return null;").softNewLine();
         writer.outdent().append("} else if (" + type + ".$meta.item) {").indent().softNewLine();
         writer.append("var arr = $rt_createArray(" + type + ".$meta.item, " + obj + ".length);").softNewLine();
         writer.append("for (var i = 0; i < arr.data.length; ++i) {").indent().softNewLine();
diff --git a/html4j/src/test/java/org/teavm/html4j/test/JavaScriptTCKTest.java b/html4j/src/test/java/org/teavm/html4j/test/JavaScriptTCKTest.java
index 47e1763d5..48022a357 100644
--- a/html4j/src/test/java/org/teavm/html4j/test/JavaScriptTCKTest.java
+++ b/html4j/src/test/java/org/teavm/html4j/test/JavaScriptTCKTest.java
@@ -56,12 +56,12 @@ public class JavaScriptTCKTest extends JavaScriptBodyTest {
 
     @Test @Override
     public void callbackUnknownArray() {
-//        super.callbackUnknownArray();
+        super.callbackUnknownArray();
     }
 
     @Test @Override
     public void callbackUnknown() {
-//        super.callbackUnknown();
+        super.callbackUnknown();
     }
 
     @Test @Override
@@ -71,7 +71,7 @@ public class JavaScriptTCKTest extends JavaScriptBodyTest {
 
     @Test @Override
     public void returnUnknownArray() {
-//        super.returnUnknownArray();
+        super.returnUnknownArray();
     }
 
     @Test @Override
@@ -81,7 +81,7 @@ public class JavaScriptTCKTest extends JavaScriptBodyTest {
 
     @Test @Override
     public void returnUnknown() {
-//        super.returnUnknown();
+        super.returnUnknown();
     }
 
     @Test @Override
@@ -236,7 +236,7 @@ public class JavaScriptTCKTest extends JavaScriptBodyTest {
 
     @Test @Override
     public void toStringOfAnEnum() {
-//        super.toStringOfAnEnum();
+        //super.toStringOfAnEnum();
     }
 
     @Test @Override