diff --git a/app/blueprints/users/account.py b/app/blueprints/users/account.py
index 79c0d0f..b8de274 100644
--- a/app/blueprints/users/account.py
+++ b/app/blueprints/users/account.py
@@ -26,7 +26,8 @@ from wtforms.validators import *
 
 from app.models import *
 from app.tasks.emails import send_verify_email, send_anon_email, send_unsubscribe_verify, send_user_email
-from app.utils import randomString, make_flask_login_password, is_safe_url, check_password_hash, addAuditLog, nonEmptyOrNone, post_login
+from app.utils import randomString, make_flask_login_password, is_safe_url, check_password_hash, addAuditLog, \
+	nonEmptyOrNone, post_login, is_username_valid
 from passlib.pwd import genphrase
 
 from . import bp
@@ -114,6 +115,10 @@ def handle_register(form):
 		flash(gettext("Incorrect captcha answer"), "danger")
 		return
 
+	if not is_username_valid(form.username.data):
+		flash(gettext("Username is invalid"))
+		return
+
 	user_by_name = User.query.filter(or_(
 			User.username == form.username.data,
 			User.username == form.display_name.data,
diff --git a/app/blueprints/users/claim.py b/app/blueprints/users/claim.py
index c994ff6..a53b633 100644
--- a/app/blueprints/users/claim.py
+++ b/app/blueprints/users/claim.py
@@ -18,15 +18,9 @@ from flask_babel import gettext
 from . import bp
 from flask import redirect, render_template, session, request, flash, url_for
 from app.models import db, User, UserRank
-from app.utils import randomString, login_user_set_active
+from app.utils import randomString, login_user_set_active, is_username_valid
 from app.tasks.forumtasks import checkForumAccount
 from app.utils.phpbbparser import getProfile
-import re
-
-
-def check_username(username):
-	return username is not None and len(username) >= 2 and re.match("^[A-Za-z0-9._-]*$", username)
-
 
 
 @bp.route("/user/claim/", methods=["GET", "POST"])
@@ -42,7 +36,7 @@ def claim_forums():
 	else:
 		method = request.args.get("method")
 
-		if not check_username(username):
+		if not is_username_valid(username):
 			flash(gettext("Invalid username - must only contain A-Za-z0-9._. Consider contacting an admin"), "danger")
 			return redirect(url_for("users.claim_forums"))
 
@@ -67,7 +61,7 @@ def claim_forums():
 		ctype	= request.form.get("claim_type")
 		username = request.form.get("username")
 
-		if not check_username(username):
+		if not is_username_valid(username):
 			flash(gettext("Invalid username - must only contain A-Za-z0-9._. Consider contacting an admin"), "danger")
 		elif ctype == "github":
 			task = checkForumAccount.delay(username)
diff --git a/app/tasks/forumtasks.py b/app/tasks/forumtasks.py
index 785e4c3..4edcc81 100644
--- a/app/tasks/forumtasks.py
+++ b/app/tasks/forumtasks.py
@@ -18,6 +18,7 @@
 import json, re, sys
 from app.models import *
 from app.tasks import celery
+from app.utils import is_username_valid
 from app.utils.phpbbparser import getProfile, getTopicsFromForum
 import urllib.request
 
@@ -137,6 +138,9 @@ def importTopicList():
 		if user:
 			return user
 
+		if not is_username_valid(username):
+			return None
+
 		user = User.query.filter_by(forums_username=username).first()
 		if user is None:
 			user = User.query.filter_by(username=username).first()
diff --git a/app/utils/__init__.py b/app/utils/__init__.py
index ed84ed4..60284df 100644
--- a/app/utils/__init__.py
+++ b/app/utils/__init__.py
@@ -19,11 +19,16 @@ import secrets
 from .flask import *
 from .models import *
 from .user import *
+import re
 
 
 YESES = ["yes", "true", "1", "on"]
 
 
+def is_username_valid(username):
+	return username is not None and len(username) >= 2 and re.match(r"^[A-Za-z0-9._-]*$", username)
+
+
 def isYes(val):
 	return val and val.lower() in YESES