diff --git a/Lib/poplib.py b/Lib/poplib.py
index be78b3e..aa4600c 100644
--- a/Lib/poplib.py
+++ b/Lib/poplib.py
@@ -240,7 +240,7 @@
 
 
     def rset(self):
-        """Not sure what this does."""
+        """Unmark all messages marked for deletion."""
         return self._shortcmd('RSET')