diff --git a/utils.py b/utils.py
index 8f4a02a6e..a8aa5416f 100644
--- a/utils.py
+++ b/utils.py
@@ -718,7 +718,7 @@ def deletePost(baseDir: str, httpPrefix: str,
 
 
 def validNickname(domain: str, nickname: str) -> bool:
-    forbiddenChars = ('.', ' ', '/', '?', ':', ';', '@')
+    forbiddenChars = ('.', ' ', '/', '?', ':', ';', '@', '#')
     for c in forbiddenChars:
         if c in nickname:
             return False