--- a/intl/uconv/nsTextToSubURI.cpp
+++ b/intl/uconv/nsTextToSubURI.cpp
@@ -235,21 +235,20 @@ NS_IMETHODIMP  nsTextToSubURI::UnEscapeU
   }
 
   // If there are any characters that are unsafe for URIs, reescape those.
   if (mUnsafeChars.IsEmpty()) {
     nsAdoptingString blacklist;
     nsresult rv = mozilla::Preferences::GetString("network.IDN.blacklist_chars",
                                                   &blacklist);
     if (NS_SUCCEEDED(rv)) {
-      nsAString& chars = blacklist;
       // we allow SPACE and IDEOGRAPHIC SPACE in this method
-      chars.StripChars(u" \u3000");
-      mUnsafeChars.AppendElements(static_cast<const char16_t*>(chars.Data()),
-                                  chars.Length());
+      blacklist.StripChars(u" \u3000");
+      mUnsafeChars.AppendElements(static_cast<const char16_t*>(blacklist.Data()),
+                                  blacklist.Length());
     } else {
       NS_WARNING("Failed to get the 'network.IDN.blacklist_chars' preference");
     }
     // We check IsEmpty() intentionally here because an empty (or just spaces)
     // pref value is likely a mistake/error of some sort.
     if (mUnsafeChars.IsEmpty()) {
       mUnsafeChars.AppendElements(sNetworkIDNBlacklistChars,
                                   mozilla::ArrayLength(sNetworkIDNBlacklistChars));

--- a/xpcom/string/nsTString.h
+++ b/xpcom/string/nsTString.h
@@ -363,16 +363,19 @@ public:
 
 
   /**
    *  These methods are used to remove all occurrences of the
    *  characters found in aSet from this string.
    *
    *  @param  aSet -- characters to be cut from this
    */
+#ifdef CharT_is_PRUnichar
+  using nsTSubstring_CharT::StripChars;
+#endif
   void StripChars(const char* aSet);
 
 
   /**
    *  This method strips whitespace throughout the string.
    */
   void StripWhitespace();
 

--- a/xpcom/tests/gtest/TestStrings.cpp
+++ b/xpcom/tests/gtest/TestStrings.cpp
@@ -811,18 +811,17 @@ TEST(String, parse_string)
   test_parse_string_helper0("", '_');
   test_parse_string_helper0("  ", ' ');
   test_parse_string_helper1(" foo", ' ', "foo");
   test_parse_string_helper1("  foo", ' ', "foo");
 }
 
 static void test_strip_chars_helper(const char16_t* str, const char16_t* strip, const nsAString& result, uint32_t offset=0)
 {
-  nsAutoString tmp(str);
-  nsAString& data = tmp;
+  nsAutoString data(str);
   data.StripChars(strip, offset);
   EXPECT_TRUE(data.Equals(result));
 }
 
 TEST(String, strip_chars)
 {
   test_strip_chars_helper(u"foo \r \nbar",
                           u" \n\r",