--- a/dom/security/sanitizer/Sanitizer.cpp
+++ b/dom/security/sanitizer/Sanitizer.cpp
@@ -42,42 +42,50 @@ already_AddRefed<Sanitizer> Sanitizer::C
   AutoTArray<nsString, 1> params = {};
   sanitizer->LogLocalizedString("SanitizerOptionsDiscarded", params,
                                 nsIScriptError::infoFlag);
   return sanitizer.forget();
 }
 
 /* static */
 already_AddRefed<DocumentFragment> Sanitizer::InputToNewFragment(
-    const mozilla::dom::StringOrDocumentFragmentOrDocument& aInput,
+    const Optional<mozilla::dom::StringOrDocumentFragmentOrDocument>& aInput,
     ErrorResult& aRv) {
   // turns an StringOrDocumentFragmentOrDocument into a DocumentFragment for
   // internal use with nsTreeSanitizer
 
   nsCOMPtr<nsPIDOMWindowInner> window = do_QueryInterface(mGlobal);
   if (!window || !window->GetDoc()) {
     // FIXME: Should we throw another exception?
     aRv.Throw(NS_ERROR_FAILURE);
     return nullptr;
   }
+  if (!aInput.WasPassed()) {
+    AutoTArray<nsString, 1> params = {};
+    LogLocalizedString("SanitizerRcvdNoInput", params,
+                       nsIScriptError::warningFlag);
 
+    RefPtr<DocumentFragment> emptyFragment =
+        window->GetDoc()->CreateDocumentFragment();
+    return emptyFragment.forget();
+  }
   // We need to create a new docfragment based on the input
   // and can't use a live document (possibly with mutation observershandlers)
   nsAutoString innerHTML;
-  if (aInput.IsDocumentFragment()) {
-    RefPtr<DocumentFragment> inFragment = &aInput.GetAsDocumentFragment();
+  if (aInput.Value().IsDocumentFragment()) {
+    RefPtr<DocumentFragment> inFragment =
+        &aInput.Value().GetAsDocumentFragment();
     inFragment->GetInnerHTML(innerHTML);
-  } else if (aInput.IsString()) {
-    innerHTML.Assign(aInput.GetAsString());
-  } else if (aInput.IsDocument()) {
-    RefPtr<Document> doc = &aInput.GetAsDocument();
+  } else if (aInput.Value().IsString()) {
+    innerHTML.Assign(aInput.Value().GetAsString());
+  } else if (aInput.Value().IsDocument()) {
+    RefPtr<Document> doc = &aInput.Value().GetAsDocument();
     nsCOMPtr<Element> docElement = doc->GetDocumentElement();
-    if (docElement) {
-      docElement->GetInnerHTML(innerHTML, IgnoreErrors());
-    }
+
+    docElement->GetInnerHTML(innerHTML, IgnoreErrors());
   }
   if (innerHTML.IsEmpty()) {
     AutoTArray<nsString, 1> params = {};
     LogLocalizedString("SanitizerRcvdNoInput", params,
                        nsIScriptError::warningFlag);
 
     RefPtr<DocumentFragment> emptyFragment =
         window->GetDoc()->CreateDocumentFragment();
@@ -95,39 +103,53 @@ already_AddRefed<DocumentFragment> Sanit
   if (aRv.Failed()) {
     aRv.Throw(NS_ERROR_FAILURE);
     return nullptr;
   }
   return fragment.forget();
 }
 
 already_AddRefed<DocumentFragment> Sanitizer::Sanitize(
-    const mozilla::dom::StringOrDocumentFragmentOrDocument& aInput,
+    const Optional<mozilla::dom::StringOrDocumentFragmentOrDocument>& aInput,
     ErrorResult& aRv) {
   nsCOMPtr<nsPIDOMWindowInner> window = do_QueryInterface(mGlobal);
   if (!window || !window->GetDoc()) {
     aRv.Throw(NS_ERROR_FAILURE);
     return nullptr;
   }
+  if (!aInput.WasPassed()) {
+    AutoTArray<nsString, 1> params = {};
+    LogLocalizedString("SanitizerRcvdNoInput", params,
+                       nsIScriptError::warningFlag);
+    RefPtr<DocumentFragment> fragment =
+        window->GetDoc()->CreateDocumentFragment();
+    return fragment.forget();
+  }
   ErrorResult error;
   RefPtr<DocumentFragment> fragment =
       Sanitizer::InputToNewFragment(aInput, error);
   if (error.Failed()) {
     return fragment.forget();
   }
   nsTreeSanitizer treeSanitizer(mSanitizationFlags);
 
   treeSanitizer.Sanitize(fragment);
   return fragment.forget();
 }
 
 void Sanitizer::SanitizeToString(
-    const StringOrDocumentFragmentOrDocument& aInput, nsAString& outSanitized,
-    ErrorResult& aRv) {
+    const Optional<StringOrDocumentFragmentOrDocument>& aInput,
+    nsAString& outSanitized, ErrorResult& aRv) {
   outSanitized.Truncate();
+  if (!aInput.WasPassed()) {
+    AutoTArray<nsString, 1> params = {};
+    LogLocalizedString("SanitizerRcvdNoInput", params,
+                       nsIScriptError::warningFlag);
+    return;
+  }
   ErrorResult error;
   RefPtr<DocumentFragment> fragment =
       Sanitizer::InputToNewFragment(aInput, error);
   if (error.Failed()) {
     return;
   }
   nsTreeSanitizer treeSanitizer(mSanitizationFlags);
 

--- a/dom/security/sanitizer/Sanitizer.h
+++ b/dom/security/sanitizer/Sanitizer.h
@@ -54,40 +54,41 @@ class Sanitizer final : public nsISuppor
       ErrorResult& aRv);
 
   /**
    * sanitize WebIDL method.
    * @param aInput       "bad" HTML that needs to be sanitized
    * @return DocumentFragment of the sanitized HTML
    */
   already_AddRefed<DocumentFragment> Sanitize(
-      const mozilla::dom::StringOrDocumentFragmentOrDocument& aInput,
+      const Optional<mozilla::dom::StringOrDocumentFragmentOrDocument>& aInput,
       ErrorResult& aRv);
 
   /**
    * sanitizeToString WebIDL method.
    * @param aInput       "bad" HTML that needs to be sanitized
    * @param outSanitized out-param for the string of sanitized HTML
    */
-  void SanitizeToString(const StringOrDocumentFragmentOrDocument& aInput,
-                        nsAString& outSanitized, ErrorResult& aRv);
+  void SanitizeToString(
+      const Optional<StringOrDocumentFragmentOrDocument>& aInput,
+      nsAString& outSanitized, ErrorResult& aRv);
 
   /**
    * Logs localized message to either content console or browser console
    * @param aName              Localization key
    * @param aParams            Localization parameters
    * @param aFlags             Logging Flag (see nsIScriptError)
    */
   void LogLocalizedString(const char* aName, const nsTArray<nsString>& aParams,
                           uint32_t aFlags);
 
  private:
   ~Sanitizer() = default;
   already_AddRefed<DocumentFragment> InputToNewFragment(
-      const mozilla::dom::StringOrDocumentFragmentOrDocument& aInput,
+      const Optional<mozilla::dom::StringOrDocumentFragmentOrDocument>& aInput,
       ErrorResult& aRv);
   /**
    * Logs localized message to either content console or browser console
    * @param aMessage           Message to log
    * @param aFlags             Logging Flag (see nsIScriptError)
    * @param aInnerWindowID     Inner Window ID (Logged on browser console if 0)
    * @param aFromPrivateWindow If from private window
    */

--- a/dom/webidl/Sanitizer.webidl
+++ b/dom/webidl/Sanitizer.webidl
@@ -19,12 +19,12 @@ dictionary SanitizerOptions {
   sequence<DOMString> removed;
 };
 
 [Exposed=Window, SecureContext, Pref="dom.security.sanitizer.enabled"]
 interface Sanitizer {
   [Throws]
   constructor(optional SanitizerOptions options = {}); // optionality still discussed in spec
   [Throws]
-  DocumentFragment sanitize(SanitizerInput input);
+  DocumentFragment sanitize(optional SanitizerInput input);
   [Throws]
-  DOMString sanitizeToString(SanitizerInput input);
+  DOMString sanitizeToString(optional SanitizerInput input);
 };