diff --git a/mozilla/dom/src/json/nsJSON.cpp b/mozilla/dom/src/json/nsJSON.cpp
index 6ad3e1f62ac..93e3190a52f 100644
--- a/mozilla/dom/src/json/nsJSON.cpp
+++ b/mozilla/dom/src/json/nsJSON.cpp
@@ -417,7 +417,7 @@ nsJSON::ToJSON(JSContext *cx, jsval *vp)
 {
   // Now we check to see whether the return value implements toJSON()
   JSBool ok = JS_TRUE;
-  char *toJSON = "toJSON";
+  const char *toJSON = "toJSON";
 
   if (!JSVAL_IS_PRIMITIVE(*vp)) {
     JSObject *obj = JSVAL_TO_OBJECT(*vp);
@@ -537,8 +537,13 @@ nsJSONWriter::Write(const PRUnichar *aBuffer, PRUint32 aLength)
     mBufferCount = 0;
   }
 
-  memcpy(&mBuffer[mBufferCount], aBuffer, aLength * sizeof(PRUnichar));
-  mBufferCount += aLength;
+  if (JSON_PARSER_BUFSIZE <= aLength) {
+    // we know mBufferCount is 0 because we know we hit the if above
+    mOutputString.Append(aBuffer, aLength);
+  } else {
+    memcpy(&mBuffer[mBufferCount], aBuffer, aLength * sizeof(PRUnichar));
+    mBufferCount += aLength;
+  }
 
   return NS_OK;
 }
diff --git a/mozilla/dom/src/json/test/unit/test_long_input.js b/mozilla/dom/src/json/test/unit/test_long_input.js
index b42a9b5a347..6b4e701c840 100644
--- a/mozilla/dom/src/json/test/unit/test_long_input.js
+++ b/mozilla/dom/src/json/test/unit/test_long_input.js
@@ -14,7 +14,8 @@ var x = {"Lorem ipsum his ponderum delicatissimi ne, at noster dolores urbanitas
 "14Lorem ipsum his ponderum delicatissimi ne, at noster dolores urbanitas pro, cibo elaboraret no his. Ea dicunt maiorum usu. Ad appareat facilisis mediocritatem eos. Tale graeci mentitum in eos, hinc insolens at nam. Graecis nominavi aliquyam eu vix.":"Id solet assentior sadipscing pro. Et per atqui graecis, usu quot viris repudiandae ei, mollis evertitur an nam. At nam dolor ignota, liber labore omnesque ea mei, has movet voluptaria in. Vel an impetus omittantur. Vim movet option salutandi ex, ne mei ignota corrumpit. Mucius comprehensam id per. Est ea putant maiestatis.",
 "15Lorem ipsum his ponderum delicatissimi ne, at noster dolores urbanitas pro, cibo elaboraret no his. Ea dicunt maiorum usu. Ad appareat facilisis mediocritatem eos. Tale graeci mentitum in eos, hinc insolens at nam. Graecis nominavi aliquyam eu vix.":"Id solet assentior sadipscing pro. Et per atqui graecis, usu quot viris repudiandae ei, mollis evertitur an nam. At nam dolor ignota, liber labore omnesque ea mei, has movet voluptaria in. Vel an impetus omittantur. Vim movet option salutandi ex, ne mei ignota corrumpit. Mucius comprehensam id per. Est ea putant maiestatis.",
 "16Lorem ipsum his ponderum delicatissimi ne, at noster dolores urbanitas pro, cibo elaboraret no his. Ea dicunt maiorum usu. Ad appareat facilisis mediocritatem eos. Tale graeci mentitum in eos, hinc insolens at nam. Graecis nominavi aliquyam eu vix.":"Id solet assentior sadipscing pro. Et per atqui graecis, usu quot viris repudiandae ei, mollis evertitur an nam. At nam dolor ignota, liber labore omnesque ea mei, has movet voluptaria in. Vel an impetus omittantur. Vim movet option salutandi ex, ne mei ignota corrumpit. Mucius comprehensam id per. Est ea putant maiestatis.",
-"17Lorem ipsum his ponderum delicatissimi ne, at noster dolores urbanitas pro, cibo elaboraret no his. Ea dicunt maiorum usu. Ad appareat facilisis mediocritatem eos. Tale graeci mentitum in eos, hinc insolens at nam. Graecis nominavi aliquyam eu vix.":"Id solet assentior sadipscing pro. Et per atqui graecis, usu quot viris repudiandae ei, mollis evertitur an nam. At nam dolor ignota, liber labore omnesque ea mei, has movet voluptaria in. Vel an impetus omittantur. Vim movet option salutandi ex, ne mei ignota corrumpit. Mucius comprehensam id per. Est ea putant maiestatis."
+"17Lorem ipsum his ponderum delicatissimi ne, at noster dolores urbanitas pro, cibo elaboraret no his. Ea dicunt maiorum usu. Ad appareat facilisis mediocritatem eos. Tale graeci mentitum in eos, hinc insolens at nam. Graecis nominavi aliquyam eu vix.":"Id solet assentior sadipscing pro. Et per atqui graecis, usu quot viris repudiandae ei, mollis evertitur an nam. At nam dolor ignota, liber labore omnesque ea mei, has movet voluptaria in. Vel an impetus omittantur. Vim movet option salutandi ex, ne mei ignota corrumpit. Mucius comprehensam id per. Est ea putant maiestatis.",
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 }
 
 var y = nativeJSON.encode(x);