diff --git a/src/main/java/fr/univ_lille/gitlab/classrooms/gitlab/GitlabApiFactory.java b/src/main/java/fr/univ_lille/gitlab/classrooms/gitlab/GitlabApiFactory.java
index d65adb8..4c72fc6 100644
--- a/src/main/java/fr/univ_lille/gitlab/classrooms/gitlab/GitlabApiFactory.java
+++ b/src/main/java/fr/univ_lille/gitlab/classrooms/gitlab/GitlabApiFactory.java
@@ -1,8 +1,11 @@
 package fr.univ_lille.gitlab.classrooms.gitlab;
 
 import fr.univ_lille.gitlab.classrooms.users.ClassroomUser;
-import org.gitlab4j.api.Constants;
+import org.gitlab4j.models.Constants;
 import org.gitlab4j.api.GitLabApi;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.security.oauth2.client.ClientAuthorizationRequiredException;
 import org.springframework.security.oauth2.client.OAuth2AuthorizeRequest;
 import org.springframework.security.oauth2.client.OAuth2AuthorizedClientManager;
 import org.springframework.stereotype.Component;
@@ -14,6 +17,8 @@ class GitlabApiFactory {
 
     private final OAuth2AuthorizedClientManager oAuth2AuthorizedClientManager;
 
+    private static final Logger LOGGER = LoggerFactory.getLogger(GitlabApiFactory.class);
+
     public GitlabApiFactory(GitlabProperties gitlabProperties, OAuth2AuthorizedClientManager oAuth2AuthorizedClientManager) {
         this.gitlabProperties = gitlabProperties;
         this.oAuth2AuthorizedClientManager = oAuth2AuthorizedClientManager;
@@ -21,18 +26,25 @@ class GitlabApiFactory {
 
     /**
      * Builds a Gitlab Api client using the credentials of the given classroom user.
+     *
      * @param user
      * @return
      */
-    public GitLabApi userGitlabApi(ClassroomUser user){
+    public GitLabApi userGitlabApi(ClassroomUser user) {
         var oauth2AuthorizedRequest = OAuth2AuthorizeRequest
                 .withClientRegistrationId("gitlab")
                 .principal(user.getName())
                 .build();
         var client = new GitLabApi(gitlabProperties.url(), Constants.TokenType.OAUTH2_ACCESS, "");
         client.setAuthTokenSupplier(() -> {
-            var oauth2Client = oAuth2AuthorizedClientManager.authorize(oauth2AuthorizedRequest);
-            return oauth2Client.getAccessToken().getTokenValue();
+            try {
+                var oauth2Client = oAuth2AuthorizedClientManager.authorize(oauth2AuthorizedRequest);
+                LOGGER.debug("Access token for user '{}' is {}", user.getName(), oauth2Client.getAccessToken().getTokenValue());
+                return oauth2Client.getAccessToken().getTokenValue();
+            } catch (ClientAuthorizationRequiredException e) {
+                LOGGER.error("Unable to get an access token for user '{}'", user.getName());
+                throw new GitLabAuthenticationException("Unable to get an access token for user '%s'".formatted(user.getName()));
+            }
         });
         return client;
     }