diff --git a/jdk-annotations/javax/swing/annotations.xml b/jdk-annotations/javax/swing/annotations.xml
index a500b7e7abb..f4fb7ec8b4b 100644
--- a/jdk-annotations/javax/swing/annotations.xml
+++ b/jdk-annotations/javax/swing/annotations.xml
@@ -263,9 +263,15 @@
     <item name='javax.swing.JMenuBar java.lang.String getUIClassID()'>
         <annotation name='org.jetbrains.annotations.NotNull'/>
     </item>
+    <item name='javax.swing.JMenuBar javax.swing.JMenu add(javax.swing.JMenu) 0'>
+        <annotation name='org.jetbrains.annotations.NotNull'/>
+    </item>
     <item name='javax.swing.JPopupMenu javax.swing.JMenuItem add(javax.swing.Action)'>
         <annotation name='org.jetbrains.annotations.NotNull'/>
     </item>
+    <item name='javax.swing.JPopupMenu javax.swing.JMenuItem add(javax.swing.JMenuItem) 0'>
+        <annotation name='org.jetbrains.annotations.NotNull'/>
+    </item>
     <item name='javax.swing.JEditorPane JEditorPane(java.net.URL) 0'>
         <annotation name='org.jetbrains.annotations.NotNull'/>
     </item>
@@ -626,6 +632,9 @@
     <item name='javax.swing.JMenu java.awt.Component add(java.awt.Component) 0'>
         <annotation name='org.jetbrains.annotations.NotNull'/>
     </item>
+    <item name='javax.swing.JMenu javax.swing.JMenuItem add(javax.swing.JMenuItem) 0'>
+        <annotation name='org.jetbrains.annotations.NotNull'/>
+    </item>
     <item name='javax.swing.JRootPane javax.swing.JLayeredPane createLayeredPane()'>
         <annotation name='org.jetbrains.annotations.NotNull'/>
     </item>
diff --git a/libraries/examples/browser-example/src/main/kotlin/sample/Hello.kt b/libraries/examples/browser-example/src/main/kotlin/sample/Hello.kt
index c301a6662d5..4848e236b0a 100644
--- a/libraries/examples/browser-example/src/main/kotlin/sample/Hello.kt
+++ b/libraries/examples/browser-example/src/main/kotlin/sample/Hello.kt
@@ -5,6 +5,6 @@ import kotlin.browser.document
 fun myApp() {
     val element = document.getElementById("foo")
     if (element != null) {
-        element.appendChild(document.createTextNode("Some Dynamically Created Content!!!"))
+        element.appendChild(document.createTextNode("Some Dynamically Created Content!!!")!!)
     }
 }
diff --git a/libraries/kotlin-swing/src/main/kotlin/kotlin/swing/ActionListeners.kt b/libraries/kotlin-swing/src/main/kotlin/kotlin/swing/ActionListeners.kt
index b5c5c050c0f..be012a85714 100644
--- a/libraries/kotlin-swing/src/main/kotlin/kotlin/swing/ActionListeners.kt
+++ b/libraries/kotlin-swing/src/main/kotlin/kotlin/swing/ActionListeners.kt
@@ -13,7 +13,7 @@ import java.awt.*
 inline fun actionListener(fn: (ActionEvent) -> Unit): ActionListener = FunctionActionListener(fn)
 
 private class FunctionActionListener(val fn: (ActionEvent) -> Unit) : ActionListener {
-    public override fun actionPerformed(e: ActionEvent?) {
+    public override fun actionPerformed(e: ActionEvent) {
         if (e != null) {
             (fn)(e)
         }
diff --git a/libraries/kotlin-swing/src/main/kotlin/kotlin/swing/Actions.kt b/libraries/kotlin-swing/src/main/kotlin/kotlin/swing/Actions.kt
index e2e96e647ce..8ce71659b33 100644
--- a/libraries/kotlin-swing/src/main/kotlin/kotlin/swing/Actions.kt
+++ b/libraries/kotlin-swing/src/main/kotlin/kotlin/swing/Actions.kt
@@ -11,7 +11,7 @@ import javax.swing.Icon
  */
 fun action(text: String, description: String? = null, mnemonic: Int? = null, icon: Icon? = null, fn: (ActionEvent) -> Unit): Action {
     val answer = object: AbstractAction(text, icon) {
-        public override fun actionPerformed(e: ActionEvent?) {
+        public override fun actionPerformed(e: ActionEvent) {
             val event: ActionEvent = if (e != null) {
                 e
             } else {
diff --git a/libraries/kotlin-swing/src/main/kotlin/kotlin/swing/ChangeListeners.kt b/libraries/kotlin-swing/src/main/kotlin/kotlin/swing/ChangeListeners.kt
index 0ec6ac8b812..6b651267132 100644
--- a/libraries/kotlin-swing/src/main/kotlin/kotlin/swing/ChangeListeners.kt
+++ b/libraries/kotlin-swing/src/main/kotlin/kotlin/swing/ChangeListeners.kt
@@ -16,7 +16,7 @@ import javax.swing.text.*
 inline fun changeListener(fn: (ChangeEvent) -> Unit): ChangeListener = FunctionChangeListener(fn)
 
 private class FunctionChangeListener(val fn: (ChangeEvent) -> Unit) : ChangeListener {
-    public override fun stateChanged(e: ChangeEvent?) {
+    public override fun stateChanged(e: ChangeEvent) {
         if (e != null) {
             (fn)(e)
         }
diff --git a/libraries/kotlin-swing/src/main/kotlin/kotlin/swing/Frames.kt b/libraries/kotlin-swing/src/main/kotlin/kotlin/swing/Frames.kt
index f2ca4004063..8fdeaf8c221 100644
--- a/libraries/kotlin-swing/src/main/kotlin/kotlin/swing/Frames.kt
+++ b/libraries/kotlin-swing/src/main/kotlin/kotlin/swing/Frames.kt
@@ -21,7 +21,7 @@ var JFrame.defaultCloseOperation: Int
 var JFrame.contentPane: Container?
     get() = getContentPane()
     set(value) {
-        setContentPane(value)
+        setContentPane(value!!)
     }
 
 var JFrame.title: String