diff --git a/src/serializer.js b/src/serializer.js
index 251f11c7..30d24fcd 100644
--- a/src/serializer.js
+++ b/src/serializer.js
@@ -251,7 +251,7 @@ export class Serializer {
     return this.statementsToN3(f.statements)
   }
 
-  _notQNameChars = '\t\r\n !"#$%&\'()*.,+/;<=>?@[\\]^`{|}~'
+  _notQNameChars = '\t\r\n !"#$%&\'()*,+/;<=>?@[\\]^`{|}~' // issue#228
   _notNameChars =
     (this._notQNameChars + ':')