diff --git a/build-config.js b/build-config.js
index 2a9b504ed7..0bb645dec3 100644
--- a/build-config.js
+++ b/build-config.js
@@ -37,7 +37,7 @@ module.exports = {
 	config: {
 		toolbar: {
 			items: [
-				'headings',
+				'heading',
 				'|',
 				'bold',
 				'italic',
@@ -51,7 +51,7 @@ module.exports = {
 		},
 
 		image: {
-			toolbar: [ 'imageStyleFull', 'imageStyleSide', '|', 'imageTextAlternative' ]
+			toolbar: [ 'imageStyle:full', 'imageStyle:side', '|', 'imageTextAlternative' ]
 		},
 
 		// UI language. Language codes follow the https://en.wikipedia.org/wiki/ISO_639-1 format.
diff --git a/src/ckeditor.js b/src/ckeditor.js
index 91e652c518..d24f932745 100644
--- a/src/ckeditor.js
+++ b/src/ckeditor.js
@@ -45,7 +45,7 @@ ClassicEditor.build = {
 	config: {
 		toolbar: {
 			items: [
-				'headings',
+				'heading',
 				'|',
 				'bold',
 				'italic',
@@ -59,8 +59,8 @@ ClassicEditor.build = {
 		},
 		image: {
 			toolbar: [
-				'imageStyleFull',
-				'imageStyleSide',
+				'imageStyle:full',
+				'imageStyle:side',
 				'|',
 				'imageTextAlternative'
 			]