diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/ir/IrBuilder.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/ir/IrBuilder.kt
index b872ab61dbd..c2a942f3941 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/ir/IrBuilder.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/ir/IrBuilder.kt
@@ -15,6 +15,7 @@ import org.jetbrains.kotlin.descriptors.Visibility
 import org.jetbrains.kotlin.ir.IrElement
 import org.jetbrains.kotlin.ir.IrStatement
 import org.jetbrains.kotlin.ir.UNDEFINED_OFFSET
+import org.jetbrains.kotlin.ir.builders.Scope
 import org.jetbrains.kotlin.ir.declarations.*
 import org.jetbrains.kotlin.ir.declarations.impl.IrFunctionImpl
 import org.jetbrains.kotlin.ir.declarations.impl.IrTypeParameterImpl
@@ -289,3 +290,30 @@ fun IrClass.simpleFunctions(): List<IrSimpleFunction> = this.declarations.flatMa
         else -> emptyList()
     }
 }
+
+fun Scope.createTmpVariable(
+    irExpression: IrExpression,
+    nameHint: String? = null,
+    isMutable: Boolean = false,
+    origin: IrDeclarationOrigin = IrDeclarationOrigin.IR_TEMPORARY_VARIABLE,
+    irType: IrType? = null
+): IrVariable {
+    val varType = irType ?: irExpression.type
+    val descriptor = WrappedVariableDescriptor()
+    val symbol = IrVariableSymbolImpl(descriptor)
+    return IrVariableImpl(
+        irExpression.startOffset,
+        irExpression.endOffset,
+        origin,
+        symbol,
+        Name.identifier(nameHint ?: "tmp"),
+        varType,
+        isMutable,
+        false,
+        false
+    ).apply {
+        initializer = irExpression
+        parent = getLocalDeclarationParent()
+        descriptor.bind(this)
+    }
+}
\ No newline at end of file
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/AutoboxingTransformer.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/AutoboxingTransformer.kt
index 1ab4ec4b049..5da5cde71e3 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/AutoboxingTransformer.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/AutoboxingTransformer.kt
@@ -62,7 +62,7 @@ class AutoboxingTransformer(val context: JsIrBackendContext) : AbstractValueUsag
         }
 
         // // TODO: Default parameters are passed as nulls and they need not to be unboxed. Fix this
-        if (actualType.makeNotNull().isNothing())
+        if (actualType.makeNotNull(false).isNothing())
             return this
 
         val expectedType = type
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/EnumClassLowering.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/EnumClassLowering.kt
index 38540c6bac6..55a65610e2a 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/EnumClassLowering.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/EnumClassLowering.kt
@@ -18,6 +18,7 @@ import org.jetbrains.kotlin.ir.IrStatement
 import org.jetbrains.kotlin.ir.UNDEFINED_OFFSET
 import org.jetbrains.kotlin.ir.backend.js.JsIrBackendContext
 import org.jetbrains.kotlin.ir.backend.js.ir.JsIrBuilder
+import org.jetbrains.kotlin.ir.backend.js.ir.createTmpVariable
 import org.jetbrains.kotlin.ir.builders.*
 import org.jetbrains.kotlin.ir.declarations.*
 import org.jetbrains.kotlin.ir.declarations.impl.IrConstructorImpl
@@ -286,10 +287,10 @@ class EnumClassTransformer(val context: JsIrBackendContext, private val irClass:
     }
 
     private fun createEnumEntryInstanceVariables() = enumEntries.map { enumEntry ->
-        val type = enumEntry.getType(irClass).makeNullable()
+        val type = enumEntry.getType(irClass).makeNullable(false)
         val name = "${enumName}_${enumEntry.name.identifier}_instance"
         builder.run {
-            scope.createTemporaryVariable(irImplicitCast(irNull(), type), name)
+            scope.createTmpVariable(irImplicitCast(irNull(), type), name)
         }
     }
 
diff --git a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/calls/EqualityAndComparisonCallsTransformer.kt b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/calls/EqualityAndComparisonCallsTransformer.kt
index ef60724ef92..20f2e8dea9c 100644
--- a/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/calls/EqualityAndComparisonCallsTransformer.kt
+++ b/compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/calls/EqualityAndComparisonCallsTransformer.kt
@@ -15,7 +15,6 @@ import org.jetbrains.kotlin.ir.expressions.impl.IrCallImpl
 import org.jetbrains.kotlin.ir.types.*
 import org.jetbrains.kotlin.ir.util.*
 import org.jetbrains.kotlin.name.Name
-import org.jetbrains.kotlin.types.isNullable
 
 
 class EqualityAndComparisonCallsTransformer(context: JsIrBackendContext) : CallsTransformer {
@@ -93,7 +92,7 @@ class EqualityAndComparisonCallsTransformer(context: JsIrBackendContext) : Calls
             isLhsPrimitive && lhsJsType == rhsJsType && lhsJsType != PrimitiveType.FLOATING_POINT_NUMBER ->
                 chooseEqualityOperatorForPrimitiveTypes(call)
 
-            !isLhsPrimitive && !lhs.type.toKotlinType().isNullable() && equalsMethod != null ->
+            !isLhsPrimitive && !lhs.type.isNullable() && equalsMethod != null ->
                 irCall(call, equalsMethod.symbol, firstArgumentAsDispatchReceiver = true)
 
             else ->