diff --git a/js/js.translator/src/org/jetbrains/kotlin/js/facade/K2JSTranslator.java b/js/js.translator/src/org/jetbrains/kotlin/js/facade/K2JSTranslator.java
index 72fbd880593..bc750f3c9e2 100644
--- a/js/js.translator/src/org/jetbrains/kotlin/js/facade/K2JSTranslator.java
+++ b/js/js.translator/src/org/jetbrains/kotlin/js/facade/K2JSTranslator.java
@@ -30,6 +30,7 @@ import org.jetbrains.kotlin.js.inline.clean.RemoveUnusedImportsKt;
 import org.jetbrains.kotlin.js.inline.clean.ResolveTemporaryNamesKt;
 import org.jetbrains.kotlin.js.translate.general.AstGenerationResult;
 import org.jetbrains.kotlin.js.translate.general.Translation;
+import org.jetbrains.kotlin.js.translate.utils.ExpandIsCallsKt;
 import org.jetbrains.kotlin.progress.ProgressIndicatorAndCompilationCanceledStatus;
 import org.jetbrains.kotlin.psi.KtFile;
 import org.jetbrains.kotlin.resolve.BindingTrace;
@@ -93,7 +94,7 @@ public final class K2JSTranslator {
         ProgressIndicatorAndCompilationCanceledStatus.checkCanceled();
         if (hasError(diagnostics)) return new TranslationResult.Fail(diagnostics);
 
-        //expandIsCalls(program, context);
+        ExpandIsCallsKt.expandIsCalls(translationResult.getFragments());
         ProgressIndicatorAndCompilationCanceledStatus.checkCanceled();
 
         List<String> importedModules = new ArrayList<>();
diff --git a/js/js.translator/src/org/jetbrains/kotlin/js/translate/context/Namer.java b/js/js.translator/src/org/jetbrains/kotlin/js/translate/context/Namer.java
index 0725ef68695..26d73003077 100644
--- a/js/js.translator/src/org/jetbrains/kotlin/js/translate/context/Namer.java
+++ b/js/js.translator/src/org/jetbrains/kotlin/js/translate/context/Namer.java
@@ -201,21 +201,16 @@ public final class Namer {
     @NotNull
     private final JsExpression callSetProperty;
 
-    @NotNull
-    private final JsName isTypeName;
-
     private Namer(@NotNull JsScope rootScope) {
         kotlinScope = new JsObjectScope(rootScope, "Kotlin standard object");
 
         callGetProperty = kotlin("callGetter");
         callSetProperty = kotlin("callSetter");
-
-        isTypeName = kotlinScope.declareName("isType");
     }
 
     // TODO: get rid of this function
     @NotNull
-    public static String getStableMangledNameForDescriptor(@NotNull ClassDescriptor descriptor, @NotNull String functionName) {
+    private static String getStableMangledNameForDescriptor(@NotNull ClassDescriptor descriptor, @NotNull String functionName) {
         Collection<SimpleFunctionDescriptor> functions = descriptor.getDefaultType().getMemberScope().getContributedFunctions(
                 Name.identifier(functionName), NoLookupLocation.FROM_BACKEND);
         assert functions.size() == 1 : "Can't select a single function: " + functionName + " in " + descriptor;
@@ -318,8 +313,8 @@ public final class Namer {
     }
 
     @NotNull
-    public JsExpression isInstanceOf(@NotNull JsExpression instance, @NotNull JsExpression type) {
-        JsInvocation result = new JsInvocation(kotlin(isTypeName), instance, type);
+    public static JsExpression isInstanceOf(@NotNull JsExpression instance, @NotNull JsExpression type) {
+        JsInvocation result = new JsInvocation(new JsNameRef("isType", KOTLIN_NAME), instance, type);
         MetadataProperties.setSideEffects(result, SideEffectKind.PURE);
         return result;
     }
diff --git a/js/js.translator/src/org/jetbrains/kotlin/js/translate/utils/expandIsCalls.kt b/js/js.translator/src/org/jetbrains/kotlin/js/translate/utils/expandIsCalls.kt
index d652976064f..fa9915fe5e7 100644
--- a/js/js.translator/src/org/jetbrains/kotlin/js/translate/utils/expandIsCalls.kt
+++ b/js/js.translator/src/org/jetbrains/kotlin/js/translate/utils/expandIsCalls.kt
@@ -20,15 +20,19 @@ import org.jetbrains.kotlin.js.backend.ast.*
 import org.jetbrains.kotlin.js.backend.ast.metadata.TypeCheck
 import org.jetbrains.kotlin.js.backend.ast.metadata.typeCheck
 import org.jetbrains.kotlin.js.inline.util.IdentitySet
-import org.jetbrains.kotlin.js.translate.context.TranslationContext
+import org.jetbrains.kotlin.js.translate.context.Namer
 import org.jetbrains.kotlin.js.translate.utils.JsAstUtils.*
 import java.util.*
 
-fun expandIsCalls(node: JsNode, context: TranslationContext) {
-    TypeCheckRewritingVisitor(context).accept(node)
+fun expandIsCalls(fragments: List<JsProgramFragment>) {
+    val visitor = TypeCheckRewritingVisitor()
+    for (fragment in fragments) {
+        visitor.accept(fragment.declarationBlock)
+        visitor.accept(fragment.initializerBlock)
+    }
 }
 
-private class TypeCheckRewritingVisitor(private val context: TranslationContext) : JsVisitorWithContextImpl() {
+private class TypeCheckRewritingVisitor : JsVisitorWithContextImpl() {
 
     private val scopes = Stack<JsScope>()
     private val localVars = Stack<MutableSet<JsName>>().apply { push(mutableSetOf()) }
@@ -78,7 +82,7 @@ private class TypeCheckRewritingVisitor(private val context: TranslationContext)
 
             TypeCheck.INSTANCEOF -> {
                 // `Kotlin.isInstanceOf(calleeArgument)(argument)` -> `argument instanceof calleeArgument`
-                if (calleeArguments.size == 1) context.namer().isInstanceOf(argument, calleeArguments[0]) else null
+                if (calleeArguments.size == 1) Namer.isInstanceOf(argument, calleeArguments[0]) else null
             }
 
             TypeCheck.OR_NULL -> {