--- a/js/src/jstracer.cpp
+++ b/js/src/jstracer.cpp
@@ -148,17 +148,17 @@ jitstats_getProperty(JSContext *cx, JSOb
         return JS_TRUE;
     }
 
     if (result < JSVAL_INT_MAX) {
         *vp = INT_TO_JSVAL(result);
         return JS_TRUE;
     }
     char retstr[64];
-    snprintf(retstr, JS_ARRAY_LENGTH(retstr), "%llu", result);
+    JS_snprintf(retstr, sizeof retstr, "%llu", result);
     *vp = STRING_TO_JSVAL(JS_NewStringCopyZ(cx, retstr));
     return JS_TRUE;
 }
 
 JSClass jitstats_class = {
     "jitstats",
     JSCLASS_HAS_PRIVATE,
     JS_PropertyStub,       JS_PropertyStub,