diff --git a/types/ckeditor/ckeditor-tests.ts b/types/ckeditor/ckeditor-tests.ts
index 1321d5b83d..13f6268d9d 100644
--- a/types/ckeditor/ckeditor-tests.ts
+++ b/types/ckeditor/ckeditor-tests.ts
@@ -620,6 +620,7 @@ function test_filter() {
     allowed = filter.allow('rule', 'name', false);
 
     var apply: boolean = filter.applyTo(CKEDITOR.htmlParser.fragment.fromHtml('string'), true, false, 1);
+    apply = filter.applyTo(new CKEDITOR.htmlParser.element('name', null));
     apply = filter.applyTo(new CKEDITOR.htmlParser.element('name', null), true, false, 1);
 
     var checked: boolean = filter.check(style);
diff --git a/types/ckeditor/index.d.ts b/types/ckeditor/index.d.ts
index 3d35877b9d..bf2d51b3db 100644
--- a/types/ckeditor/index.d.ts
+++ b/types/ckeditor/index.d.ts
@@ -1436,7 +1436,7 @@ declare namespace CKEDITOR {
         addFeature(feature: feature): boolean;
         addTransformations(transformations: Array<Array<string | filter.transformation>>): void;
         allow(newRules: filter.allowedContentRules, featureName?: string, overrideCustom?: boolean): boolean;
-        applyTo(fragment: htmlParser.fragment | htmlParser.element, toHrml: boolean, transformOnly: boolean, enterMode: number): boolean;
+        applyTo(fragment: htmlParser.fragment | htmlParser.element, toHtml?: boolean, transformOnly?: boolean, enterMode?: number): boolean;
         check(test: filter.contentRule, applyTransformations?: boolean, strictCheck?: boolean): boolean;
         checkFeature(feature: feature): boolean;
         clone(): filter;