diff --git a/js/js.tests/test/org/jetbrains/k2js/test/semantics/CastTest.java b/js/js.tests/test/org/jetbrains/k2js/test/semantics/CastTest.java
new file mode 100644
index 00000000000..7dee4df742c
--- /dev/null
+++ b/js/js.tests/test/org/jetbrains/k2js/test/semantics/CastTest.java
@@ -0,0 +1,34 @@
+/*
+ * Copyright 2010-2013 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.jetbrains.k2js.test.semantics;
+
+/**
+ * A messy class where all new tests go before they are sorted which never happens.
+ */
+public final class CastTest extends AbstractExpressionTest {
+    public CastTest() {
+        super("cast/");
+    }
+
+    public void testCastToNullableType() throws Exception {
+        checkFooBoxIsOk();
+    }
+
+    public void testCastToNotNullType() throws Exception {
+        checkFooBoxIsOk();
+    }
+}
diff --git a/js/js.translator/src/org/jetbrains/k2js/translate/expression/ExpressionVisitor.java b/js/js.translator/src/org/jetbrains/k2js/translate/expression/ExpressionVisitor.java
index b366416ebed..de1740379eb 100644
--- a/js/js.translator/src/org/jetbrains/k2js/translate/expression/ExpressionVisitor.java
+++ b/js/js.translator/src/org/jetbrains/k2js/translate/expression/ExpressionVisitor.java
@@ -24,8 +24,10 @@ import org.jetbrains.jet.lang.descriptors.FunctionDescriptor;
 import org.jetbrains.jet.lang.descriptors.VariableDescriptor;
 import org.jetbrains.jet.lang.psi.*;
 import org.jetbrains.jet.lang.resolve.BindingContext;
+import org.jetbrains.jet.lang.resolve.BindingContextUtils;
 import org.jetbrains.jet.lang.resolve.constants.CompileTimeConstant;
 import org.jetbrains.jet.lang.resolve.constants.NullValue;
+import org.jetbrains.jet.lexer.JetTokens;
 import org.jetbrains.k2js.translate.context.TemporaryVariable;
 import org.jetbrains.k2js.translate.context.TranslationContext;
 import org.jetbrains.k2js.translate.declaration.ClassTranslator;
@@ -36,6 +38,7 @@ import org.jetbrains.k2js.translate.operation.BinaryOperationTranslator;
 import org.jetbrains.k2js.translate.operation.UnaryOperationTranslator;
 import org.jetbrains.k2js.translate.reference.*;
 import org.jetbrains.k2js.translate.utils.BindingUtils;
+import org.jetbrains.k2js.translate.utils.TranslationUtils;
 import org.jetbrains.k2js.translate.utils.mutator.AssignToExpressionMutator;
 
 import java.util.Collections;
@@ -311,9 +314,19 @@ public final class ExpressionVisitor extends TranslatorVisitor<JsNode> {
     @NotNull
     public JsNode visitBinaryWithTypeRHSExpression(@NotNull JetBinaryExpressionWithTypeRHS expression,
             @NotNull TranslationContext context) {
+        JsExpression jsExpression = Translation.translateAsExpression(expression.getLeft(), context);
+
+        if (expression.getOperationReference().getReferencedNameElementType() != JetTokens.AS_KEYWORD)
+            return jsExpression;
+
+        JetTypeReference type = expression.getRight();
+        assert type != null;
+        if (BindingContextUtils.getNotNull(context.bindingContext(), BindingContext.TYPE, type).isNullable())
+            return jsExpression;
+
         // KT-2670
         // we actually do not care for types in js
-        return Translation.translateExpression(expression.getLeft(), context);
+        return TranslationUtils.sure(jsExpression, context);
     }
 
     @Override
diff --git a/js/js.translator/testFiles/expression/cast/cases/castToNotNullType.kt b/js/js.translator/testFiles/expression/cast/cases/castToNotNullType.kt
new file mode 100644
index 00000000000..3f838834b24
Binary files /dev/null and b/js/js.translator/testFiles/expression/cast/cases/castToNotNullType.kt differ
diff --git a/js/js.translator/testFiles/expression/cast/cases/castToNullableType.kt b/js/js.translator/testFiles/expression/cast/cases/castToNullableType.kt
new file mode 100644
index 00000000000..ad6d812f265
Binary files /dev/null and b/js/js.translator/testFiles/expression/cast/cases/castToNullableType.kt differ