diff --git a/idea/src/org/jetbrains/kotlin/idea/refactoring/introduce/extractClass/ui/KotlinExtractSuperclassDialog.kt b/idea/src/org/jetbrains/kotlin/idea/refactoring/introduce/extractClass/ui/KotlinExtractSuperclassDialog.kt
index 66ab24beaa4..31c88409edd 100644
--- a/idea/src/org/jetbrains/kotlin/idea/refactoring/introduce/extractClass/ui/KotlinExtractSuperclassDialog.kt
+++ b/idea/src/org/jetbrains/kotlin/idea/refactoring/introduce/extractClass/ui/KotlinExtractSuperclassDialog.kt
@@ -1,17 +1,6 @@
 /*
- * Copyright 2010-2016 JetBrains s.r.o.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
+ * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
  */
 
 package org.jetbrains.kotlin.idea.refactoring.introduce.extractClass.ui
@@ -67,13 +56,13 @@ class KotlinExtractSuperclassDialog(
 
     override fun getDestinationPackageRecentKey() = DESTINATION_PACKAGE_RECENT_KEY
 
-    override fun getClassNameLabelText() = RefactoringBundle.message("superclass.name")!!
+    override fun getClassNameLabelText(): String = RefactoringBundle.message("superclass.name")
 
-    override fun getPackageNameLabelText() = RefactoringBundle.message("package.for.new.superclass")!!
+    override fun getPackageNameLabelText(): String = RefactoringBundle.message("package.for.new.superclass")
 
-    override fun getEntityName() = RefactoringBundle.message("ExtractSuperClass.superclass")!!
+    override fun getEntityName(): String = RefactoringBundle.message("ExtractSuperClass.superclass")
 
-    override fun getTopLabelText() = RefactoringBundle.message("extract.superclass.from")!!
+    override fun getTopLabelText(): String = RefactoringBundle.message("extract.superclass.from")
 
     override fun getDocCommentPolicySetting() = KotlinRefactoringSettings.instance.EXTRACT_SUPERCLASS_JAVADOC
 
@@ -81,7 +70,7 @@ class KotlinExtractSuperclassDialog(
         KotlinRefactoringSettings.instance.EXTRACT_SUPERCLASS_JAVADOC = policy
     }
 
-    override fun getExtractedSuperNameNotSpecifiedMessage() = RefactoringBundle.message("no.superclass.name.specified")!!
+    override fun getExtractedSuperNameNotSpecifiedMessage(): String = RefactoringBundle.message("no.superclass.name.specified")
 
     override fun getHelpId() = HelpID.EXTRACT_SUPERCLASS
 }
\ No newline at end of file