--- a/netwerk/streamconv/converters/nsDirIndexParser.cpp
+++ b/netwerk/streamconv/converters/nsDirIndexParser.cpp
@@ -3,17 +3,19 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 /* This parsing code originally lived in xpfe/components/directory/ - bbaetz */
 
 #include "nsDirIndexParser.h"
 
 #include "mozilla/ArrayUtils.h"
+#include "mozilla/ClearOnShutdown.h"
 #include "mozilla/Encoding.h"
+#include "mozilla/StaticPtr.h"
 #include "prprf.h"
 #include "nsCRT.h"
 #include "nsDirIndex.h"
 #include "nsEscape.h"
 #include "nsIDirIndex.h"
 #include "nsIInputStream.h"
 #include "nsITextToSubURI.h"
 #include "nsServiceManagerUtils.h"
@@ -21,16 +23,18 @@
 
 using namespace mozilla;
 
 struct EncodingProp {
   const char* const mKey;
   NotNull<const Encoding*> mValue;
 };
 
+static StaticRefPtr<nsITextToSubURI> gTextToSubURI;
+
 static const EncodingProp localesFallbacks[] = {
     {"ar", WINDOWS_1256_ENCODING}, {"ba", WINDOWS_1251_ENCODING},
     {"be", WINDOWS_1251_ENCODING}, {"bg", WINDOWS_1251_ENCODING},
     {"cs", WINDOWS_1250_ENCODING}, {"el", ISO_8859_7_ENCODING},
     {"et", WINDOWS_1257_ENCODING}, {"fa", WINDOWS_1256_ENCODING},
     {"he", WINDOWS_1255_ENCODING}, {"hr", WINDOWS_1250_ENCODING},
     {"hu", ISO_8859_2_ENCODING},   {"ja", SHIFT_JIS_ENCODING},
     {"kk", WINDOWS_1251_ENCODING}, {"ko", EUC_KR_ENCODING},
@@ -85,34 +89,29 @@ NS_IMPL_ISUPPORTS(nsDirIndexParser, nsIR
 
 nsresult nsDirIndexParser::Init() {
   mLineStart = 0;
   mHasDescription = false;
   mFormat[0] = -1;
   auto encoding = GetFTPFallbackEncodingDoNotAddNewCallersToThisFunction();
   encoding->Name(mEncoding);
 
-  nsresult rv;
-  // XXX not threadsafe
-  if (gRefCntParser++ == 0) {
-    rv = CallGetService(NS_ITEXTTOSUBURI_CONTRACTID, &gTextToSubURI);
-  } else {
-    rv = NS_OK;
+  nsresult rv = NS_OK;
+  if (!gTextToSubURI) {
+    nsCOMPtr<nsITextToSubURI> service =
+        do_GetService(NS_ITEXTTOSUBURI_CONTRACTID, &rv);
+    if (NS_SUCCEEDED(rv)) {
+      gTextToSubURI = service;
+      ClearOnShutdown(&gTextToSubURI);
+    }
   }
 
   return rv;
 }
 
-nsDirIndexParser::~nsDirIndexParser() {
-  // XXX not threadsafe
-  if (--gRefCntParser == 0) {
-    NS_IF_RELEASE(gTextToSubURI);
-  }
-}
-
 NS_IMETHODIMP
 nsDirIndexParser::SetListener(nsIDirIndexListener* aListener) {
   mListener = aListener;
   return NS_OK;
 }
 
 NS_IMETHODIMP
 nsDirIndexParser::GetListener(nsIDirIndexListener** aListener) {
@@ -161,19 +160,16 @@ nsDirIndexParser::Field nsDirIndexParser
     {"Filename", FIELD_FILENAME},
     {"Description", FIELD_DESCRIPTION},
     {"Content-Length", FIELD_CONTENTLENGTH},
     {"Last-Modified", FIELD_LASTMODIFIED},
     {"Content-Type", FIELD_CONTENTTYPE},
     {"File-Type", FIELD_FILETYPE},
     {nullptr, FIELD_UNKNOWN}};
 
-nsrefcnt nsDirIndexParser::gRefCntParser = 0;
-nsITextToSubURI* nsDirIndexParser::gTextToSubURI = nullptr;
-
 void nsDirIndexParser::ParseFormat(const char* aFormatStr) {
   // Parse a "200" format line, and remember the fields and their
   // ordering in mFormat. Multiple 200 lines stomp on each other.
   unsigned int formatNum = 0;
   mFormat[0] = -1;
 
   do {
     while (*aFormatStr && nsCRT::IsAsciiSpace(char16_t(*aFormatStr))) {
@@ -276,20 +272,20 @@ void nsDirIndexParser::ParseData(nsIDirI
       case FIELD_FILENAME: {
         // don't unescape at this point, so that UnEscapeAndConvert() can
         filename = value;
 
         bool success = false;
 
         nsAutoString entryuri;
 
-        if (gTextToSubURI) {
+        if (RefPtr<nsITextToSubURI> textToSub = gTextToSubURI) {
           nsAutoString result;
-          if (NS_SUCCEEDED(gTextToSubURI->UnEscapeAndConvert(
-                  mEncoding, filename, result))) {
+          if (NS_SUCCEEDED(
+                  textToSub->UnEscapeAndConvert(mEncoding, filename, result))) {
             if (!result.IsEmpty()) {
               aIdx->SetLocation(filename);
               if (!mHasDescription) aIdx->SetDescription(result);
               success = true;
             }
           } else {
             NS_WARNING("UnEscapeAndConvert error");
           }

--- a/netwerk/streamconv/converters/nsDirIndexParser.h
+++ b/netwerk/streamconv/converters/nsDirIndexParser.h
@@ -13,17 +13,17 @@
 
 class nsIDirIndex;
 class nsITextToSubURI;
 
 /* CID: {a0d6ad32-1dd1-11b2-aa55-a40187b54036} */
 
 class nsDirIndexParser : public nsIDirIndexParser {
  private:
-  virtual ~nsDirIndexParser();
+  virtual ~nsDirIndexParser() = default;
 
   nsDirIndexParser() = default;
   nsresult Init();
 
  public:
   NS_DECL_ISUPPORTS
   NS_DECL_NSISTREAMLISTENER
   NS_DECL_NSIREQUESTOBSERVER
@@ -62,14 +62,11 @@ class nsDirIndexParser : public nsIDirIn
   void ParseData(nsIDirIndex* aIdx, char* aDataStr, int32_t lineLen);
 
   struct Field {
     const char* mName;
     fieldType mType;
   };
 
   static Field gFieldTable[];
-
-  static nsrefcnt gRefCntParser;
-  static nsITextToSubURI* gTextToSubURI;
 };
 
 #endif