diff --git a/netwerk/base/nsStandardURL.cpp b/netwerk/base/nsStandardURL.cpp
index 6d6d647588c1..e1b30fe98b0a 100644
--- a/netwerk/base/nsStandardURL.cpp
+++ b/netwerk/base/nsStandardURL.cpp
@@ -781,8 +781,7 @@ nsStandardURL::BuildNormalizedSpec(const char *spec,
     // approxLen should be correct or 1 high
     if (!mSpec.SetLength(approxLen+1, fallible)) // buf needs a trailing '\0' below
         return NS_ERROR_OUT_OF_MEMORY;
-    char *buf;
-    mSpec.BeginWriting(buf);
+    char *buf = mSpec.BeginWriting();
     uint32_t i = 0;
     int32_t diff = 0;
 
diff --git a/xpcom/io/nsLocalFileCommon.cpp b/xpcom/io/nsLocalFileCommon.cpp
index dc749cb7689e..a815a5dd62f3 100644
--- a/xpcom/io/nsLocalFileCommon.cpp
+++ b/xpcom/io/nsLocalFileCommon.cpp
@@ -220,10 +220,8 @@ nsLocalFile::GetRelativeDescriptor(nsIFile* aFromFile, nsACString& aResult)
   }
 
   // get raw pointer to mutable string buffer
-  char16_t* thisPathPtr;
-  thisPath.BeginWriting(thisPathPtr);
-  char16_t* fromPathPtr;
-  fromPath.BeginWriting(fromPathPtr);
+  char16_t* thisPathPtr = thisPath.BeginWriting();
+  char16_t* fromPathPtr = fromPath.BeginWriting();
 
   SplitPath(thisPathPtr, thisNodes);
   SplitPath(fromPathPtr, fromNodes);
diff --git a/xpcom/string/nsTSubstring.h b/xpcom/string/nsTSubstring.h
index addee96cfa8f..140b5b1a77d3 100644
--- a/xpcom/string/nsTSubstring.h
+++ b/xpcom/string/nsTSubstring.h
@@ -393,26 +393,6 @@ public:
     return EnsureMutable() ? (base_string_type::mData + base_string_type::mLength) : iterator(0);
   }
 
-  iterator& BeginWriting(iterator& aIter)
-  {
-    return aIter = BeginWriting();
-  }
-
-  iterator& BeginWriting(iterator& aIter, const fallible_t& aFallible)
-  {
-    return aIter = BeginWriting(aFallible);
-  }
-
-  iterator& EndWriting(iterator& aIter)
-  {
-    return aIter = EndWriting();
-  }
-
-  iterator& EndWriting(iterator& aIter, const fallible_t& aFallible)
-  {
-    return aIter = EndWriting(aFallible);
-  }
-
   /**
    * Perform string to int conversion.
    * @param   aErrorCode will contain error if one occurs