diff --git a/extensions/spellcheck/myspell/src/csutil.cpp b/extensions/spellcheck/myspell/src/csutil.cpp
index 1803bd6af7ab..7487dbc13e26 100644
--- a/extensions/spellcheck/myspell/src/csutil.cpp
+++ b/extensions/spellcheck/myspell/src/csutil.cpp
@@ -212,7 +212,7 @@ struct cs_info * get_current_cs(const char * es) {
   if (NS_FAILED(rv))
     return nsnull;
 
-  ccs = (struct cs_info *) malloc(0xff * sizeof(cs_info));
+  ccs = (struct cs_info *) malloc(256 * sizeof(cs_info));
 
   PRInt32 charLength = 256;
   PRInt32 uniLength = 512;