diff --git a/core/style.js b/core/style.js
index a14e1d4c7fc..29fca312fb1 100644
--- a/core/style.js
+++ b/core/style.js
@@ -1204,6 +1204,9 @@ CKEDITOR.STYLE_OBJECT = 3;
 			// The 'class' element value must match (#1318).
 			if ( ( attName == 'class' || this._.definition.fullMatch ) && element.getAttribute( attName ) != normalizeProperty( attName, attributes[ attName ] ) )
 				continue;
+			// Do not touch data-* attributes (#11011).
+			if ( attName.substr( 0, 5 ) == 'data-' )
+				continue;
 			removeEmpty = element.hasAttribute( attName );
 			element.removeAttribute( attName );
 		}