diff --git a/Astral.Services/Interfaces/IUserService.cs b/Astral.Services/Interfaces/IUserService.cs
index a0f8e5b..7b9958c 100644
--- a/Astral.Services/Interfaces/IUserService.cs
+++ b/Astral.Services/Interfaces/IUserService.cs
@@ -23,5 +23,5 @@ public interface IUserService
     /// </summary>
     /// <param name="userId">User id.</param>
     /// <returns>Instance of <see cref="UserDto" />, or null if not found.</returns>
-    Task<UserDto> FindById(string userId);
+    Task<UserDto> FindById(Guid userId);
 }
diff --git a/Astral.Services/Services/UserService.cs b/Astral.Services/Services/UserService.cs
index 5e3ea94..1b1d747 100644
--- a/Astral.Services/Services/UserService.cs
+++ b/Astral.Services/Services/UserService.cs
@@ -45,7 +45,7 @@ public class UserService : IUserService
     /// <param name="createUserValidator">Instance of <see cref="CreateUserValidator" />.</param>
     /// <param name="registrationConfig">Instance of <see cref="IOptions{RegistrationOptions}" />.</param>
     /// <param name="transactionProvider">Instance of <see cref="ITransactionProvider" />.</param>
-    /// <param name="transactionProvider">Instance of <see cref="ITransactionProvider" />.</param>
+    /// <param name="userProfileRepository">Instance of <see cref="IUserProfileRepository" />.</param>
     /// <param name="logger">Instance of <see cref="ILogger" />.</param>
     public UserService(
         IUserRepository userRepository,
@@ -154,14 +154,9 @@ public class UserService : IUserService
     }
 
     /// <inheritdoc />
-    public async Task<UserDto> FindById(string userId)
+    public async Task<UserDto> FindById(Guid userId)
     {
-        if (!Guid.TryParse(userId, out var userGuid))
-        {
-            return null;
-        }
-
-        var user = await _userRepository.FindByIdAsync(userGuid);
+        var user = await _userRepository.FindByIdAsync(userId);
 
         return _mapper.Map<UserDto>(user);
     }