diff --git a/plugins/font/plugin.js b/plugins/font/plugin.js
index f255488eeef..4d100257603 100644
--- a/plugins/font/plugin.js
+++ b/plugins/font/plugin.js
@@ -174,7 +174,7 @@
 					if ( previousStyle ) {
 						editor.removeStyle( previousStyle );
 					}
-				} else if ( value !== previousValue ) {
+				} else {
 					editor.applyStyle( style );
 				}
 
diff --git a/tests/plugins/font/font.js b/tests/plugins/font/font.js
index c281b773975..fff6a59e71e 100644
--- a/tests/plugins/font/font.js
+++ b/tests/plugins/font/font.js
@@ -13,7 +13,8 @@
 			fixStyles: true
 		},
 		ffArial = 'font-family:Arial,Helvetica,sans-serif',
-		ffCS = 'font-family:Comic Sans MS,cursive';
+		ffCS = 'font-family:Comic Sans MS,cursive',
+		ffCourierNew = 'font-family:Courier New,Courier,monospace';
 
 	bender.test( {
 		_should: {
@@ -251,7 +252,32 @@
 					}, 0 );
 				}, 0 );
 			} );
-		}
+		},
 
+		// (#1040)
+		'test apply new style to entire selection if partially present': function() {
+			var bot = this.editorBot;
+			bender.tools.selection.setWithHtml( bot.editor, '<h1><span style="' + ffCourierNew + '">[Hello</span> world!]</h1>' );
+
+			bot.combo( 'Font', function( combo ) {
+				combo.onClick( 'Courier New' );
+				this.wait( function() {
+					assert.isInnerHtmlMatching( '<h1><span style="' + ffCourierNew + '">Hello world!</span>@</h1>', bot.editor.editable().getHtml(), htmlMatchingOpts );
+				}, 0 );
+			} );
+		},
+
+		// (#1040)
+		'test if styles are not changed if applied second time on the part of already styled element': function() {
+			var bot = this.editorBot;
+			bender.tools.selection.setWithHtml( bot.editor, '<h1><span style="' + ffCourierNew + '">[Hel]lo</span> world!</h1>' );
+
+			bot.combo( 'Font', function( combo ) {
+				combo.onClick( 'Courier New' );
+				this.wait( function() {
+					assert.isInnerHtmlMatching( '<h1><span style="' + ffCourierNew + '">Hello</span> world!@</h1>', bot.editor.editable().getHtml(), htmlMatchingOpts );
+				}, 0 );
+			} );
+		}
 	} );
 } )();
diff --git a/tests/plugins/font/manual/partialstyles.html b/tests/plugins/font/manual/partialstyles.html
new file mode 100644
index 00000000000..6d1b2ed66ca
--- /dev/null
+++ b/tests/plugins/font/manual/partialstyles.html
@@ -0,0 +1,8 @@
+<div id="editor">
+	<p>Hello world!</p>
+	<p>Hello again!</p>
+</div>
+
+<script>
+	CKEDITOR.replace( 'editor' );
+</script>
diff --git a/tests/plugins/font/manual/partialstyles.md b/tests/plugins/font/manual/partialstyles.md
new file mode 100644
index 00000000000..9531027a8ac
--- /dev/null
+++ b/tests/plugins/font/manual/partialstyles.md
@@ -0,0 +1,25 @@
+@bender-tags: 4.8.0, bug, 1040
+@bender-ui: collapsed
+@bender-ckeditor-plugins: wysiwygarea, toolbar, font, elementspath, sourcearea
+
+## Scenario 1:
+
+1. Select `Hello` word.
+2. Apply **Courier New** font.
+3. Expand selection to contain whole text line.
+4. Apply **Courier New** font.
+
+### Expected result
+
+Font has been applied to whole `Hello world!` text.
+
+## Scenario 2:
+
+1. Select `again` word.
+2. Apply **36** size.
+3. Expand selection to contain whole text line.
+4. Apply **36** size.
+
+### Expected result
+
+Size has been applied to whole `Hello again!` text.