diff --git a/src/classiceditor.js b/src/classiceditor.js
index 596cd92..5c11c7c 100644
--- a/src/classiceditor.js
+++ b/src/classiceditor.js
@@ -70,9 +70,9 @@ export default class ClassicEditor extends Editor {
 
 		this.model.document.createRoot();
 
-		const shouldGroupWhenFull = this.config.get( 'toolbar.shouldGroupWhenFull' );
+		const shouldToolbarGroupWhenFull = !this.config.get( 'toolbar.shouldNotGroupWhenFull' );
 		const view = new ClassicEditorUIView( this.locale, this.editing.view, {
-			shouldToolbarGroupWhenFull: shouldGroupWhenFull === undefined ? true : shouldGroupWhenFull
+			shouldToolbarGroupWhenFull
 		} );
 
 		this.ui = new ClassicEditorUI( this, view );
diff --git a/tests/classiceditor.js b/tests/classiceditor.js
index 0e1b121..8a0b139 100644
--- a/tests/classiceditor.js
+++ b/tests/classiceditor.js
@@ -113,11 +113,11 @@ describe( 'ClassicEditor', () => {
 					editorElement.remove();
 				} );
 
-				it( 'can be disabled using config.toolbar.shouldGroupWhenFull', () => {
+				it( 'can be disabled using config.toolbar.shouldNotGroupWhenFull', () => {
 					const editorElement = document.createElement( 'div' );
 					const editor = new ClassicEditor( editorElement, {
 						toolbar: {
-							shouldGroupWhenFull: false
+							shouldNotGroupWhenFull: true
 						}
 					} );