diff --git a/htdocs/confluence-account-review.html b/htdocs/confluence-account-review.html
index 9f27def..432e5c0 100644
--- a/htdocs/confluence-account-review.html
+++ b/htdocs/confluence-account-review.html
@@ -9,7 +9,7 @@
     <div class="mb-3">
         <label for="username" class="form-label">Desired User name</label>
         <input type="text" class="form-control" id="username" readonly name="username" aria-describedby="usernameHelp">
-        <div id="usernameHelp" class="form-text">The user name must be between 4 and 20 characters long.</div>
+        <div id="usernameHelp" class="form-text">The user name must be between 4 and 20 characters long, alphanumeric only.</div>
     </div>
     <div class="mb-3">
         <label for="realname" class="form-label">Their real (public) name</label>
diff --git a/htdocs/confluence-account.html b/htdocs/confluence-account.html
index d470919..ff397f7 100644
--- a/htdocs/confluence-account.html
+++ b/htdocs/confluence-account.html
@@ -30,7 +30,7 @@
     <div class="mb-3">
         <label for="username" class="form-label">Desired user name</label>
         <input type="text" class="form-control project-dependent" id="username" name="username" aria-describedby="usernameHelp">
-        <div id="usernameHelp" class="form-text">Your user name must be between 4 and 20 characters long.</div>
+        <div id="usernameHelp" class="form-text">Your user name must be between 4 and 20 characters long, alphanumeric only.</div>
     </div>
     <div class="mb-3">
         <label for="realname" class="form-label">Your real (public) name</label>
diff --git a/htdocs/jira-account-review.html b/htdocs/jira-account-review.html
index fcd8229..faa4041 100644
--- a/htdocs/jira-account-review.html
+++ b/htdocs/jira-account-review.html
@@ -9,7 +9,7 @@
     <div class="mb-3">
         <label for="username" class="form-label">Desired User name</label>
         <input type="text" class="form-control" id="username" readonly name="username" aria-describedby="usernameHelp">
-        <div id="usernameHelp" class="form-text">The user name must be between 4 and 20 characters long.</div>
+        <div id="usernameHelp" class="form-text">The user name must be between 4 and 20 characters long, alphanumeric only.</div>
     </div>
     <div class="mb-3">
         <label for="realname" class="form-label">Their real (public) name</label>
diff --git a/htdocs/jira-account.html b/htdocs/jira-account.html
index 78a23fd..4788084 100644
--- a/htdocs/jira-account.html
+++ b/htdocs/jira-account.html
@@ -28,7 +28,7 @@
     <div class="mb-3">
         <label for="username" class="form-label">Desired user name</label>
         <input type="text" class="form-control project-dependent" id="username" name="username" aria-describedby="usernameHelp">
-        <div id="usernameHelp" class="form-text">Your user name must be between 4 and 20 characters long.</div>
+        <div id="usernameHelp" class="form-text">Your user name must be between 4 and 20 characters long, alphanumeric only.</div>
     </div>
     <div class="mb-3">
         <label for="realname" class="form-label">Your real (public) name</label>
diff --git a/server/app/endpoints/confluenceaccount.py b/server/app/endpoints/confluenceaccount.py
index 2e893aa..4326448 100644
--- a/server/app/endpoints/confluenceaccount.py
+++ b/server/app/endpoints/confluenceaccount.py
@@ -37,7 +37,7 @@
 INFRAREPORTS_USERID_CHECK = "https://infra-reports.apache.org/api/userid"
 
 VALID_EMAIL_RE = re.compile(r"^[^@]+@[^@]+\.[^@]+$")
-VALID_CONFLUENCE_USERNAME_RE = re.compile(r"^[^<>&%\s]{4,20}$")  # 4-20 chars, no whitespace or illegal chars
+VALID_CONFLUENCE_USERNAME_RE = re.compile(r"^[^<>&%\s.]{4,20}$")  # 4-20 chars, no whitespace or illegal chars
 # Taken from com.atlassian.jira.bc.user.UserValidationHelper
 
 # It is expensive to use the ACLI to check for existing user ids
diff --git a/server/app/endpoints/jiraaccount.py b/server/app/endpoints/jiraaccount.py
index c298726..49f7928 100644
--- a/server/app/endpoints/jiraaccount.py
+++ b/server/app/endpoints/jiraaccount.py
@@ -40,7 +40,7 @@
 INFRAREPORTS_USERID_CHECK = "https://infra-reports.apache.org/api/userid"
 
 VALID_EMAIL_RE = re.compile(r"^[^@]+@[^@]+\.[^@]+$")
-VALID_JIRA_USERNAME_RE = re.compile(r"^[^<>&%\s]{4,20}$")  # 4-20 chars, no whitespace or illegal chars
+VALID_JIRA_USERNAME_RE = re.compile(r"^[^<>&%\s.]{4,20}$")  # 4-20 chars, no whitespace or illegal chars
 # Taken from com.atlassian.jira.bc.user.UserValidationHelper
 
 # It is expensive to use the Jira CLI to check for existing user ids