diff --git a/modules/security/src/main/DataForm.scala b/modules/security/src/main/DataForm.scala
index 11c5525196..c2c9673b48 100644
--- a/modules/security/src/main/DataForm.scala
+++ b/modules/security/src/main/DataForm.scala
@@ -35,7 +35,7 @@ final class DataForm(
       Constraints minLength 2,
       Constraints maxLength 20,
       Constraints.pattern(
-        regex = User.usernameRegex,
+        regex = User.newUsernameRegex,
         error = "usernameInvalid"
       )
     ).verifying("usernameUnacceptable", u => !LameName.username(u))
diff --git a/modules/user/src/main/User.scala b/modules/user/src/main/User.scala
index b8a7da0600..f97e59d985 100644
--- a/modules/user/src/main/User.scala
+++ b/modules/user/src/main/User.scala
@@ -140,8 +140,12 @@ object User {
   // No: contact@lichess.org, @1, http://example.com/@happy0
   val atUsernameRegex = """(?<=\s|^)@(?>([a-zA-Z_-][\w-]{1,19}))(?![\w-])""".r
 
-  val usernameRegex = """(?i)[a-z][\w-]*[a-z0-9]""".r
-  def couldBeUsername(str: String) = usernameRegex.pattern.matcher(str).matches
+  // what existing usernames are like
+  val historicalUsernameRegex = """(?i)[\w-]*[a-z0-9]""".r
+  // what new usernames should be like
+  val newUsernameRegex = """(?i)[a-z][\w-]*[a-z0-9]""".r
+
+  def couldBeUsername(str: String) = historicalUsernameRegex.pattern.matcher(str).matches
 
   def normalize(username: String) = username.toLowerCase