diff --git a/compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/codegen/ExpressionCodegen.kt b/compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/codegen/ExpressionCodegen.kt
index fabe9297d2c..0b22f13f4e3 100644
--- a/compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/codegen/ExpressionCodegen.kt
+++ b/compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/codegen/ExpressionCodegen.kt
@@ -528,10 +528,13 @@ class ExpressionCodegen(
                 return onStack(boxedType)
             }
 
-            IrTypeOperator.INSTANCEOF -> {
+            IrTypeOperator.INSTANCEOF, IrTypeOperator.NOT_INSTANCEOF -> {
                 gen(expression.argument, OBJECT_TYPE, data)
                 val type = boxType(asmType)
                 generateIsCheck(mv, expression.typeOperand, type)
+                if (IrTypeOperator.NOT_INSTANCEOF == expression.operator) {
+                    StackValue.not(StackValue.onStack(Type.BOOLEAN_TYPE)).put(Type.BOOLEAN_TYPE, mv)
+                }
             }
 
             IrTypeOperator.IMPLICIT_NOTNULL -> {