diff --git a/lib/naive_bayes.js b/lib/naive_bayes.js
index 15eb5b2..0270128 100644
--- a/lib/naive_bayes.js
+++ b/lib/naive_bayes.js
@@ -25,6 +25,9 @@ module.exports.fromJson = function (jsonStr) {
   } catch (e) {
     throw new Error('Naivebayes.fromJson expects a valid JSON string.')
   }
+  if (typeof parsed.options.tokenizer === 'string') {
+    parsed.options.tokenizer = eval(parsed.options.tokenizer)
+  }
   // init a new classifier
   var classifier = new Naivebayes(parsed.options)
 
@@ -265,7 +268,12 @@ Naivebayes.prototype.toJson = function () {
     state[k] = self[k]
   })
 
-  var jsonStr = JSON.stringify(state)
+  var jsonStr = JSON.stringify(state, function(key, val) {
+    if (typeof val === 'function') {
+      return val.toString()
+    }
+    return val;
+  })
 
   return jsonStr
 }