diff --git a/intl/unicharutil/src/nsSaveAsCharset.cpp b/intl/unicharutil/src/nsSaveAsCharset.cpp
index d344919a1fd..cc61f942400 100644
--- a/intl/unicharutil/src/nsSaveAsCharset.cpp
+++ b/intl/unicharutil/src/nsSaveAsCharset.cpp
@@ -236,7 +236,7 @@ nsSaveAsCharset::DoConversionFallBack(PRUnichar inCharacter, char *outString, PR
   if(nsnull == outString )
     return NS_ERROR_NULL_POINTER;
 
-  *outString = NULL;
+  *outString = '\0';
 
   nsresult rv = NS_OK;