diff --git a/Lib/CGIHTTPServer.py b/Lib/CGIHTTPServer.py
index 13bfcdd..ad49e93 100644
--- a/Lib/CGIHTTPServer.py
+++ b/Lib/CGIHTTPServer.py
@@ -76,6 +76,9 @@
         (dir, rest) if self.path requires running a CGI script.
         Returns False otherwise.
 
+        If any exception is raised, the caller should assume that
+        self.path was rejected as invalid and act accordingly.
+
         The default implementation tests whether the normalized url
         path begins with one of the strings in self.cgi_directories
         (and the next character is a '/' or the end of the string).