diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsLoweringPhases.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsLoweringPhases.kt
index 6a337443682..8953648aadf 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsLoweringPhases.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsLoweringPhases.kt
@@ -637,86 +637,6 @@ private val cleanupLoweringPhase = makeBodyLoweringPhase(
 )
 
 val loweringList = listOf<Lowering>(
-    scriptRemoveReceiverLowering,
-    validateIrBeforeLowering,
-    testGenerationPhase,
-    expectDeclarationsRemovingPhase,
-    stripTypeAliasDeclarationsPhase,
-    arrayConstructorPhase,
-    lateinitNullableFieldsPhase,
-    lateinitDeclarationLoweringPhase,
-    lateinitUsageLoweringPhase,
-    sharedVariablesLoweringPhase,
-    localClassesInInlineLambdasPhase,
-    localClassesInInlineFunctionsPhase,
-    localClassesExtractionFromInlineFunctionsPhase,
-    functionInliningPhase,
-    copyInlineFunctionBodyLoweringPhase,
-    createScriptFunctionsPhase,
-    callableReferenceLowering,
-    singleAbstractMethodPhase,
-    tailrecLoweringPhase,
-    enumClassConstructorLoweringPhase,
-    enumClassConstructorBodyLoweringPhase,
-    localDelegatedPropertiesLoweringPhase,
-    localDeclarationsLoweringPhase,
-    localClassExtractionPhase,
-    innerClassesLoweringPhase,
-    innerClassesMemberBodyLoweringPhase,
-    innerClassConstructorCallsLoweringPhase,
-    propertiesLoweringPhase,
-    primaryConstructorLoweringPhase,
-    delegateToPrimaryConstructorLoweringPhase,
-    annotationConstructorLowering,
-    initializersLoweringPhase,
-    initializersCleanupLoweringPhase,
-    kotlinNothingValueExceptionPhase,
-    // Common prefix ends
-    enumEntryInstancesLoweringPhase,
-    enumEntryInstancesBodyLoweringPhase,
-    enumClassCreateInitializerLoweringPhase,
-    enumEntryCreateGetInstancesFunsLoweringPhase,
-    enumSyntheticFunsLoweringPhase,
-    enumUsageLoweringPhase,
-    enumEntryRemovalLoweringPhase,
-    suspendFunctionsLoweringPhase,
-    propertyReferenceLoweringPhase,
-    interopCallableReferenceLoweringPhase,
-    returnableBlockLoweringPhase,
-    forLoopsLoweringPhase,
-    primitiveCompanionLoweringPhase,
-    propertyAccessorInlinerLoweringPhase,
-    foldConstantLoweringPhase,
-    privateMembersLoweringPhase,
-    privateMemberUsagesLoweringPhase,
-    defaultArgumentStubGeneratorPhase,
-    defaultArgumentPatchOverridesPhase,
-    defaultParameterInjectorPhase,
-    defaultParameterCleanerPhase,
-    jsDefaultCallbackGeneratorPhase,
-    removeInlineFunctionsWithReifiedTypeParametersLoweringPhase,
-    throwableSuccessorsLoweringPhase,
-    varargLoweringPhase,
-    multipleCatchesLoweringPhase,
-    bridgesConstructionPhase,
-    typeOperatorLoweringPhase,
-    secondaryConstructorLoweringPhase,
-    secondaryFactoryInjectorLoweringPhase,
-    classReferenceLoweringPhase,
-    inlineClassDeclarationLoweringPhase,
-    inlineClassUsageLoweringPhase,
-    autoboxingTransformerPhase,
-    blockDecomposerLoweringPhase,
-    constLoweringPhase,
-    objectDeclarationLoweringPhase,
-    objectUsageLoweringPhase,
-    captureStackTraceInThrowablesPhase,
-    callsLoweringPhase,
-    cleanupLoweringPhase,
-    validateIrAfterLowering
-)
-
-val es6LoweringList = listOf<Lowering>(
     scriptRemoveReceiverLowering,
     validateIrBeforeLowering,
     testGenerationPhase,
@@ -782,6 +702,7 @@ val es6LoweringList = listOf<Lowering>(
     multipleCatchesLoweringPhase,
     bridgesConstructionPhase,
     typeOperatorLoweringPhase,
+    secondaryConstructorLoweringPhase,
     secondaryFactoryInjectorLoweringPhase,
     classReferenceLoweringPhase,
     inlineClassDeclarationLoweringPhase,
@@ -808,11 +729,3 @@ val jsPhases = namedIrModulePhase(
         acc.then(lowering.modulePhase)
     }
 )
-
-val jsEs6Phases = namedIrModulePhase(
-    name = "ES6IrModuleLowering",
-    description = "ES6 IR module lowering",
-    lower = es6LoweringList.drop(1).fold(es6LoweringList[0].modulePhase) { acc: CompilerPhase<JsIrBackendContext, IrModuleFragment, IrModuleFragment>, lowering ->
-        acc.then(lowering.modulePhase)
-    }
-)
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/compiler.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/compiler.kt
index ce819c2c3ef..f0425dae54e 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/compiler.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/compiler.kt
@@ -98,8 +98,7 @@ fun compile(
         val transformer = IrModuleToJsTransformer(context, mainFunction, mainArguments)
         return transformer.generateModule(moduleFragment, fullJs = true, dceJs = false)
     } else {
-        val phases = if (es6mode) jsEs6Phases else jsPhases
-        phases.invokeToplevel(phaseConfig, context, moduleFragment)
+        jsPhases.invokeToplevel(phaseConfig, context, moduleFragment)
         val transformer = IrModuleToJsTransformer(context, mainFunction, mainArguments)
         return transformer.generateModule(moduleFragment, generateFullJs, generateDceJs)
     }
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/ES6AddInternalParametersToConstructorPhase.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/ES6AddInternalParametersToConstructorPhase.kt
index 7058a9018bd..8748bec0614 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/ES6AddInternalParametersToConstructorPhase.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/ES6AddInternalParametersToConstructorPhase.kt
@@ -55,7 +55,7 @@ class ES6AddInternalParametersToConstructorPhase(val context: JsIrBackendContext
     object ES6_RESULT_TYPE_PARAMETER : IrDeclarationOriginImpl("ES6_RESULT_TYPE_PARAMETER")
 
     override fun lower(irBody: IrBody, container: IrDeclaration) {
-        assert(context.es6mode)
+        if (!context.es6mode) return
 
         container.transform(CallSiteTransformer(), null)
 
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/ES6ConstructorLowering.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/ES6ConstructorLowering.kt
index 1d8660f2f9e..d3eccfb77aa 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/ES6ConstructorLowering.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/ES6ConstructorLowering.kt
@@ -29,7 +29,7 @@ object ES6_THIS_VARIABLE_ORIGIN : IrDeclarationOriginImpl("ES6_THIS_VARIABLE_ORI
 
 class ES6ConstructorLowering(val context: JsIrBackendContext) : BodyLoweringPass {
     override fun lower(irBody: IrBody, container: IrDeclaration) {
-        assert(context.es6mode)
+        if (!context.es6mode) return
 
         if (container !is IrConstructor) return
 
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/SecondaryCtorLowering.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/SecondaryCtorLowering.kt
index 52bae86fd67..54004b364ed 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/SecondaryCtorLowering.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/SecondaryCtorLowering.kt
@@ -34,7 +34,7 @@ import org.jetbrains.kotlin.ir.visitors.transformChildrenVoid
 class SecondaryConstructorLowering(val context: JsIrBackendContext) : DeclarationTransformer {
 
     override fun transformFlat(declaration: IrDeclaration): List<IrDeclaration>? {
-        assert(!context.es6mode)
+        if (context.es6mode) return null
 
         if (declaration is IrConstructor && !declaration.isPrimary) {
             val irClass = declaration.parentAsClass
diff --git a/js/js.tests/test/org/jetbrains/kotlin/js/test/BasicIrBoxTest.kt b/js/js.tests/test/org/jetbrains/kotlin/js/test/BasicIrBoxTest.kt
index f84b3a41c6d..36998041d56 100644
--- a/js/js.tests/test/org/jetbrains/kotlin/js/test/BasicIrBoxTest.kt
+++ b/js/js.tests/test/org/jetbrains/kotlin/js/test/BasicIrBoxTest.kt
@@ -107,20 +107,19 @@ abstract class BasicIrBoxTest(
         if (isMainModule) {
             val debugMode = getBoolean("kotlin.js.debugMode")
 
-            val phases = if (runEs6Mode) jsEs6Phases else jsPhases
             val phaseConfig = if (debugMode) {
-                val allPhasesSet = phases.toPhaseMap().values.toSet()
+                val allPhasesSet = jsPhases.toPhaseMap().values.toSet()
                 val dumpOutputDir = File(outputFile.parent, outputFile.nameWithoutExtension + "-irdump")
                 println("\n ------ Dumping phases to file://$dumpOutputDir")
                 PhaseConfig(
-                    phases,
+                    jsPhases,
                     dumpToDirectory = dumpOutputDir.path,
                     toDumpStateAfter = allPhasesSet,
                     toValidateStateAfter = allPhasesSet,
                     dumpOnlyFqName = null
                 )
             } else {
-                PhaseConfig(phases)
+                PhaseConfig(jsPhases)
             }
 
             if (!skipRegularMode) {