diff --git a/src/main/java/auth_service/configuration/security/JwtAuthenticationFilter.java b/src/main/java/auth_service/configuration/security/JwtAuthenticationFilter.java
index d60cbee..6c84ee3 100644
--- a/src/main/java/auth_service/configuration/security/JwtAuthenticationFilter.java
+++ b/src/main/java/auth_service/configuration/security/JwtAuthenticationFilter.java
@@ -1,5 +1,6 @@
 package auth_service.configuration.security;
 
+import auth_service.shared.security.UserPrincipal;
 import jakarta.servlet.FilterChain;
 import jakarta.servlet.ServletException;
 import jakarta.servlet.http.HttpServletRequest;
diff --git a/src/main/java/auth_service/domain/user/controller/UserController.java b/src/main/java/auth_service/domain/user/controller/UserController.java
index 66565db..61e7777 100644
--- a/src/main/java/auth_service/domain/user/controller/UserController.java
+++ b/src/main/java/auth_service/domain/user/controller/UserController.java
@@ -1,6 +1,6 @@
 package auth_service.domain.user.controller;
 
-import auth_service.configuration.security.UserPrincipal;
+import auth_service.shared.security.UserPrincipal;
 import auth_service.domain.user.controller.dto.request.UserSettingsRequest;
 import auth_service.domain.user.controller.dto.response.UserProfileResponse;
 import auth_service.domain.user.controller.mapper.ApiMapper;
diff --git a/src/main/java/auth_service/domain/user/persistence/UserRepositoryImpl.java b/src/main/java/auth_service/domain/user/persistence/UserRepositoryImpl.java
index 249bed8..5e1521a 100644
--- a/src/main/java/auth_service/domain/user/persistence/UserRepositoryImpl.java
+++ b/src/main/java/auth_service/domain/user/persistence/UserRepositoryImpl.java
@@ -61,15 +61,24 @@ public class UserRepositoryImpl implements UserRepository {
     @Transactional
     @Override
     public boolean updateSettings(long userId, long steamId, UserSettings settings) {
-        var entity = EntityMapper.toPersistence(userId, settings);
-        // merge() acts as an upsert: it updates if the ID exists, or inserts if it doesn't.
-        entityManager.merge(entity);
-
         var userEntity = entityManager.find(UserEntity.class, userId);
-        if (userEntity != null && userEntity.getSteamId() != steamId) {
-            userEntity.setSteamId(steamId);
-            return true;
+        if (userEntity == null) {
+            return false;
         }
-        return false;
+
+        var settingsEntity = userEntity.getSettings();
+        if (settingsEntity == null) {
+            settingsEntity = new UserSettingsEntity();
+            settingsEntity.setUserId(userId);
+            userEntity.setSettings(settingsEntity);
+        }
+
+        settingsEntity.setLanguage(settings.getLanguage());
+        settingsEntity.setTheme(settings.getTheme());
+
+        boolean steamIdChanged = userEntity.getSteamId() != steamId;
+        userEntity.setSteamId(steamId);
+
+        return steamIdChanged;
     }
 }
\ No newline at end of file
diff --git a/src/main/java/auth_service/domain/user/persistence/entities/UserEntity.java b/src/main/java/auth_service/domain/user/persistence/entities/UserEntity.java
index 3d5c80c..c436278 100644
--- a/src/main/java/auth_service/domain/user/persistence/entities/UserEntity.java
+++ b/src/main/java/auth_service/domain/user/persistence/entities/UserEntity.java
@@ -30,7 +30,7 @@ public class UserEntity {
     @Column(nullable = false)
     private boolean enabled;
 
-    @Column(name = "steam_id", unique = true, nullable = false)
+    @Column(name = "steam_id", unique = true)
     private Long steamId;
 
     @Column(name = "registration_date", nullable = false)
diff --git a/src/main/java/auth_service/configuration/security/UserPrincipal.java b/src/main/java/auth_service/shared/security/UserPrincipal.java
similarity index 85%
rename from src/main/java/auth_service/configuration/security/UserPrincipal.java
rename to src/main/java/auth_service/shared/security/UserPrincipal.java
index ccfa99e..20ff95f 100644
--- a/src/main/java/auth_service/configuration/security/UserPrincipal.java
+++ b/src/main/java/auth_service/shared/security/UserPrincipal.java
@@ -1,4 +1,4 @@
-package auth_service.configuration.security;
+package auth_service.shared.security;
 
 import java.security.Principal;
 
diff --git a/src/main/resources/db/migration/V2__Add_User_Details.sql b/src/main/resources/db/migration/V2__Add_User_Details.sql
index 9983b0c..3392ebb 100644
--- a/src/main/resources/db/migration/V2__Add_User_Details.sql
+++ b/src/main/resources/db/migration/V2__Add_User_Details.sql
@@ -1,6 +1,6 @@
 -- Create the users table
 ALTER TABLE users
-    ADD COLUMN steam_id BIGINT DEFAULT 0,
+    ADD COLUMN steam_id BIGINT,
     ADD COLUMN registration_date TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
     ADD COLUMN last_login_date TIMESTAMP;
 
diff --git a/src/test/java/auth_service/domain/user/controller/UserControllerTest.java b/src/test/java/auth_service/domain/user/controller/UserControllerTest.java
index 0214689..d1b66a0 100644
--- a/src/test/java/auth_service/domain/user/controller/UserControllerTest.java
+++ b/src/test/java/auth_service/domain/user/controller/UserControllerTest.java
@@ -2,7 +2,7 @@ package auth_service.domain.user.controller;
 
 import auth_service.configuration.security.JwtAuthenticationFilter;
 import auth_service.configuration.security.JwtService;
-import auth_service.configuration.security.UserPrincipal;
+import auth_service.shared.security.UserPrincipal;
 import auth_service.domain.user.controller.dto.request.UserSettingsRequest;
 import auth_service.domain.user.exception.UserNotFoundException;
 import auth_service.domain.user.model.User;
diff --git a/src/test/java/auth_service/domain/user/persistence/UserRepositoryTest.java b/src/test/java/auth_service/domain/user/persistence/UserRepositoryTest.java
index ba712d7..49a3026 100644
--- a/src/test/java/auth_service/domain/user/persistence/UserRepositoryTest.java
+++ b/src/test/java/auth_service/domain/user/persistence/UserRepositoryTest.java
@@ -24,7 +24,7 @@ class UserRepositoryTest extends AbstractPersistenceTest {
     @Test
     void findByEmail_Success() {
         // Arrange
-        var email = "test@example.com";
+        var email = "newuser@example.com";
         var userEntity = UserEntity.builder()
                 .email(email)
                 .password("password")
diff --git a/src/test/java/auth_service/shared/test/AbstractIntegrationTest.java b/src/test/java/auth_service/shared/test/AbstractIntegrationTest.java
index e0ac792..6a7a3f0 100644
--- a/src/test/java/auth_service/shared/test/AbstractIntegrationTest.java
+++ b/src/test/java/auth_service/shared/test/AbstractIntegrationTest.java
@@ -2,6 +2,7 @@ package auth_service.shared.test;
 
 import org.junit.jupiter.api.Tag;
 import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.context.ActiveProfiles;
 import org.springframework.boot.testcontainers.service.connection.ServiceConnection;
 import org.testcontainers.containers.PostgreSQLContainer;
 import org.testcontainers.junit.jupiter.Container;
@@ -13,6 +14,7 @@ import org.testcontainers.junit.jupiter.Testcontainers;
  */
 @Tag("IntegrationTest")
 @SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
+@ActiveProfiles("dev")
 @Testcontainers
 public abstract class AbstractIntegrationTest {