diff --git a/src/IRCLine.py b/src/IRCLine.py
index c0263d20..3a8f14b5 100644
--- a/src/IRCLine.py
+++ b/src/IRCLine.py
@@ -45,7 +45,7 @@ class ParsedLine(object):
         self._args = args
         self.args = IRCArgs(args)
         self.source = source
-        self.tags = {} if tags == None else tags
+        self.tags = tags or {} # type: typing.Dict[str, str]
         self._valid = True
         self._assured = False
 
@@ -64,6 +64,9 @@ class ParsedLine(object):
     def assure(self):
         self._assured = True
 
+    def add_tag(self, tag: str, value: str=None):
+        self.tags[tag] = value or ""
+
     def _tag_str(self, tags: typing.Dict[str, str]) -> str:
         tag_pieces = []
         for tag, value in tags.items():