diff --git a/API/Controllers/AccountController.cs b/API/Controllers/AccountController.cs
index 04d0bf9d5..f788f931f 100644
--- a/API/Controllers/AccountController.cs
+++ b/API/Controllers/AccountController.cs
@@ -82,7 +82,7 @@ namespace API.Controllers
         [HttpPost("register")]
         public async Task<ActionResult<UserDto>> Register(RegisterDto registerDto)
         {
-            if (await _userManager.Users.AnyAsync(x => x.UserName == registerDto.Username))
+            if (await _userManager.Users.AnyAsync(x => x.NormalizedUserName == registerDto.Username.ToUpper()))
             {
                 return BadRequest("Username is taken.");
             }