diff --git a/clientapi/routing/register.go b/clientapi/routing/register.go
index 756eafe2..90e9eed3 100644
--- a/clientapi/routing/register.go
+++ b/clientapi/routing/register.go
@@ -113,7 +113,7 @@ var (
 	// TODO: Remove old sessions. Need to do so on a session-specific timeout.
 	// sessions stores the completed flow stages for all sessions. Referenced using their sessionID.
 	sessions           = newSessionsDict()
-	validUsernameRegex = regexp.MustCompile(`^[0-9a-z_\-./]+$`)
+	validUsernameRegex = regexp.MustCompile(`^[0-9a-z_\-=./]+$`)
 )
 
 // registerRequest represents the submitted registration request.