diff --git a/intl/uconv/src/nsScriptableUConv.h b/intl/uconv/src/nsScriptableUConv.h
index 401d7d09e86..27c7a2ac880 100644
--- a/intl/uconv/src/nsScriptableUConv.h
+++ b/intl/uconv/src/nsScriptableUConv.h
@@ -54,9 +54,7 @@ public:
   virtual ~nsScriptableUnicodeConverter();
 
 protected:
-  // charsets are ALWAYS very short, so its actually better to use
-  // nsCAutoString here
-  nsCAutoString mCharset;
+  nsCString mCharset;
   nsCOMPtr<nsIUnicodeEncoder> mEncoder;
   nsCOMPtr<nsIUnicodeDecoder> mDecoder;
 
diff --git a/modules/libpref/src/nsPrefBranch.h b/modules/libpref/src/nsPrefBranch.h
index c2970197743..44330d4b368 100644
--- a/modules/libpref/src/nsPrefBranch.h
+++ b/modules/libpref/src/nsPrefBranch.h
@@ -121,6 +121,5 @@ public:
   
 private:
   nsCOMPtr<nsILocalFile> mFile;
-  nsCAutoString mRelativeToKey; // An nsCAutoString because length is always very short.
-                                // While this makes the object larger, avoids allocation.
+  nsCString mRelativeToKey;
 };
diff --git a/netwerk/base/src/nsDirectoryIndexStream.h b/netwerk/base/src/nsDirectoryIndexStream.h
index 00871a674c6..0fe473e528f 100644
--- a/netwerk/base/src/nsDirectoryIndexStream.h
+++ b/netwerk/base/src/nsDirectoryIndexStream.h
@@ -48,7 +48,7 @@
 class nsDirectoryIndexStream : public nsIInputStream
 {
 private:
-    nsCAutoString mBuf;
+    nsCString mBuf;
     PRInt32 mOffset;
     nsresult mStatus;
 
diff --git a/netwerk/streamconv/converters/nsFTPDirListingConv.h b/netwerk/streamconv/converters/nsFTPDirListingConv.h
index 257bf287caa..fa0de04f644 100644
--- a/netwerk/streamconv/converters/nsFTPDirListingConv.h
+++ b/netwerk/streamconv/converters/nsFTPDirListingConv.h
@@ -77,7 +77,7 @@ private:
     char*    DigestBufferLines(char *aBuffer, nsCString &aString);
 
     // member data
-    nsCAutoString       mBuffer;            // buffered data.
+    nsCString           mBuffer;            // buffered data.
     PRBool              mSentHeading;       // have we sent 100, 101, 200, and 300 lines yet?
 
     nsIStreamListener   *mFinalListener; // this guy gets the converted data via his OnDataAvailable()
diff --git a/xpcom/string/public/nsTString.h b/xpcom/string/public/nsTString.h
index ceb833d4cbb..3cc93b82e4d 100644
--- a/xpcom/string/public/nsTString.h
+++ b/xpcom/string/public/nsTString.h
@@ -487,7 +487,7 @@ class nsTFixedString_CharT : public nsTString_CharT
    * Subclass of nsTString_CharT that adds support for stack-based string
    * allocation.  Do not allocate this class on the heap! ;-)
    */
-class nsTAutoString_CharT : public nsTFixedString_CharT
+class NS_STACK_CLASS nsTAutoString_CharT : public nsTFixedString_CharT
   {
     public:
 
@@ -631,7 +631,7 @@ class nsTXPIDLString_CharT : public nsTString_CharT
    *      // ...
    *    }
    */
-class nsTGetterCopies_CharT
+class NS_STACK_CLASS nsTGetterCopies_CharT
   {
     public:
       typedef CharT char_type;