diff --git a/packages/ckeditor5-link/src/ui/linkformview.js b/packages/ckeditor5-link/src/ui/linkformview.js
index 32e71422773..25cb4195af0 100644
--- a/packages/ckeditor5-link/src/ui/linkformview.js
+++ b/packages/ckeditor5-link/src/ui/linkformview.js
@@ -285,7 +285,7 @@ export default class LinkFormView extends View {
 			} );
 
 			switchButton.bind( 'isOn' ).toMany( [ manualDecorator, linkCommand ], 'value', ( decoratorValue, commandValue ) => {
-				return commandValue === undefined && decoratorValue === undefined ? manualDecorator.defaultValue : decoratorValue;
+				return commandValue === false && decoratorValue === false ? manualDecorator.defaultValue : decoratorValue;
 			} );
 
 			switchButton.on( 'execute', () => {
diff --git a/packages/ckeditor5-ui/src/button/buttonview.js b/packages/ckeditor5-ui/src/button/buttonview.js
index e71a41404cc..70068dd73ea 100644
--- a/packages/ckeditor5-ui/src/button/buttonview.js
+++ b/packages/ckeditor5-ui/src/button/buttonview.js
@@ -145,7 +145,7 @@ export default class ButtonView extends View {
 				tabindex: bind.to( 'tabindex' ),
 				'aria-labelledby': `ck-editor__aria-label_${ ariaLabelUid }`,
 				'aria-disabled': bind.if( 'isEnabled', true, value => !value ),
-				'aria-pressed': bind.to( 'isOn', value => this.isToggleable ? String( value ) : false )
+				'aria-pressed': bind.to( 'isOn', value => this.isToggleable ? Boolean( value ) : false )
 			},
 
 			children: this.children,