diff --git a/js/src/com/google/dart/compiler/util/AstUtil.java b/js/src/com/google/dart/compiler/util/AstUtil.java
index a1ba71ce077..2bc025b1c21 100644
--- a/js/src/com/google/dart/compiler/util/AstUtil.java
+++ b/js/src/com/google/dart/compiler/util/AstUtil.java
@@ -269,7 +269,7 @@ public class AstUtil {
         return result;
     }
 
-    public static JsPrefixOperation negation(JsExpression expression) {
+    public static JsPrefixOperation negated(JsExpression expression) {
         return new JsPrefixOperation(JsUnaryOperator.NOT, expression);
     }
 }
diff --git a/translator/src/org/jetbrains/k2js/translate/PatternTranslator.java b/translator/src/org/jetbrains/k2js/translate/PatternTranslator.java
index d73984ddc2b..2abb504754d 100644
--- a/translator/src/org/jetbrains/k2js/translate/PatternTranslator.java
+++ b/translator/src/org/jetbrains/k2js/translate/PatternTranslator.java
@@ -46,7 +46,7 @@ public final class PatternTranslator extends AbstractTranslator {
         JetPattern pattern = getPattern(expression);
         JsExpression resultingExpression = translatePattern(pattern, left);
         if (expression.isNegated()) {
-            return AstUtil.negation(resultingExpression);
+            return AstUtil.negated(resultingExpression);
         }
         return resultingExpression;
     }
diff --git a/translator/src/org/jetbrains/k2js/translate/WhenTranslator.java b/translator/src/org/jetbrains/k2js/translate/WhenTranslator.java
index 9ad7f3205ef..86777d87df2 100644
--- a/translator/src/org/jetbrains/k2js/translate/WhenTranslator.java
+++ b/translator/src/org/jetbrains/k2js/translate/WhenTranslator.java
@@ -25,6 +25,7 @@ public class WhenTranslator extends AbstractTranslator {
     private final JsExpression expressionToMatch;
     @NotNull
     private final JsName dummyCounterName;
+    private int currentEntryNumber = 0;
 
     private WhenTranslator(@NotNull JetWhenExpression expression, @NotNull TranslationContext context) {
         super(context);
@@ -35,16 +36,27 @@ public class WhenTranslator extends AbstractTranslator {
 
     @NotNull
     JsNode translate() {
-        return translateEntries();
+        JsFor resultingFor = generateDummyFor();
+        List<JsStatement> entries = translateEntries();
+        resultingFor.setBody(AstUtil.newBlock(entries));
+        return resultingFor;
     }
 
-    private JsBlock translateEntries() {
-        //JsFor resultingFor = generateDummyFor();
+    @NotNull
+    private List<JsStatement> translateEntries() {
         List<JsStatement> entries = new ArrayList<JsStatement>();
         for (JetWhenEntry entry : whenExpression.getEntries()) {
-            entries.add(translateEntry(entry));
+            entries.add(surroundWithDummyIf(translateEntry(entry)));
         }
-        return AstUtil.newBlock(entries);
+        return entries;
+    }
+
+    @NotNull
+    private JsStatement surroundWithDummyIf(@NotNull JsStatement entryStatement) {
+        JsExpression stepNumberEqualsCurrentEntryNumber = new JsBinaryOperation(JsBinaryOperator.EQ,
+                dummyCounterName.makeRef(), translationContext().program().getNumberLiteral(currentEntryNumber));
+        currentEntryNumber++;
+        return new JsIf(stepNumberEqualsCurrentEntryNumber, entryStatement, null);
     }
 
     @NotNull
@@ -110,8 +122,12 @@ public class WhenTranslator extends AbstractTranslator {
 
     @NotNull
     private JsExpression translatePatternCondition(@NotNull JetWhenConditionIsPattern condition) {
-        return Translation.typeOperationTranslator(translationContext()).
+        JsExpression patternMatchExpression = Translation.typeOperationTranslator(translationContext()).
                 translatePattern(getPattern(condition), expressionToMatch);
+        if (condition.isNegated()) {
+            return AstUtil.negated(patternMatchExpression);
+        }
+        return patternMatchExpression;
     }
 
     @NotNull
diff --git a/translator/test/org/jetbrains/k2js/test/PatternMatchingTest.java b/translator/test/org/jetbrains/k2js/test/PatternMatchingTest.java
index 8b73a74f9df..2973f6999f7 100644
--- a/translator/test/org/jetbrains/k2js/test/PatternMatchingTest.java
+++ b/translator/test/org/jetbrains/k2js/test/PatternMatchingTest.java
@@ -19,4 +19,9 @@ public final class PatternMatchingTest extends IncludeLibraryTest {
         testFooBoxIsTrue("whenType.kt");
     }
 
+    @Test
+    public void whenNotType() throws Exception {
+        testFooBoxIsTrue("whenNotType.kt");
+    }
+
 }
diff --git a/translator/test/org/jetbrains/k2js/test/RhinoFunctionResultChecker.java b/translator/test/org/jetbrains/k2js/test/RhinoFunctionResultChecker.java
index 34a40a3ae17..8be5474e5bc 100644
--- a/translator/test/org/jetbrains/k2js/test/RhinoFunctionResultChecker.java
+++ b/translator/test/org/jetbrains/k2js/test/RhinoFunctionResultChecker.java
@@ -30,7 +30,7 @@ public final class RhinoFunctionResultChecker implements RhinoResultChecker {
     @Override
     public void runChecks(Context context, Scriptable scope) throws Exception {
         Object result = extractAndCallFunctionObject(namespaceName, functionName, context, scope);
-        assertTrue("Result is not what expected! Exprected: " + expectedResult + " Evaluated : " + result,
+        assertTrue("Result is not what expected! Expected: " + expectedResult + " Evaluated : " + result,
                 result.equals(expectedResult));
         String report = namespaceName + "." + functionName + "() = " + Context.toString(result);
         System.out.println(report);
diff --git a/translator/testFiles/patternMatching/cases/whenNotType.kt b/translator/testFiles/patternMatching/cases/whenNotType.kt
new file mode 100644
index 00000000000..be7d077a352
--- /dev/null
+++ b/translator/testFiles/patternMatching/cases/whenNotType.kt
@@ -0,0 +1,12 @@
+namespace foo
+
+class A() {
+
+}
+
+fun box() : Boolean {
+  when(A()) {
+    !is A => return false;
+    else => return true;
+  }
+}
\ No newline at end of file