diff --git a/config/ClientsSharedConfig.ts b/config/ClientsSharedConfig.ts
index ea55b0c06a35f38773c6744474159514f0687fed..77f1053b62aa98d6703a8d441e583657c24f7f5b 100644
--- a/config/ClientsSharedConfig.ts
+++ b/config/ClientsSharedConfig.ts
@@ -21,28 +21,28 @@ class ClientsSharedConfig {
 
 
     constructor() {
-        this.apiURL = process.env.API_URL || '';
+        this.apiURL = process.env.API_URL ?? '';
 
         this.assignment = {
-            filename   : process.env.ASSIGNMENT_FILENAME || '',
-            neededFiles: JSON.parse(process.env.EXERCISE_NEEDED_FILES || '[]')
+            filename   : process.env.ASSIGNMENT_FILENAME ?? '',
+            neededFiles: JSON.parse(process.env.EXERCISE_NEEDED_FILES ?? '[]')
         };
 
         this.gitlab = {
             dojoAccount: {
-                id      : Number(process.env.GITLAB_DOJO_ACCOUNT_ID) || -1,
-                username: process.env.GITLAB_DOJO_ACCOUNT_USERNAME || ''
+                id      : Number(process.env.GITLAB_DOJO_ACCOUNT_ID ?? -1),
+                username: process.env.GITLAB_DOJO_ACCOUNT_USERNAME ?? ''
             }
         };
 
         this.dockerCompose = {
-            projectName: process.env.DOCKER_COMPOSE_PROJECT_NAME || ''
+            projectName: process.env.DOCKER_COMPOSE_PROJECT_NAME ?? ''
         };
 
-        this.exerciseResultsFolderMaxSizeInBytes = Number(process.env.EXERCISE_RESULTS_FOLDER_MAX_SIZE_IN_BYTES || 0);
+        this.exerciseResultsFolderMaxSizeInBytes = Number(process.env.EXERCISE_RESULTS_FOLDER_MAX_SIZE_IN_BYTES ?? 0);
 
         this.filenames = {
-            results: process.env.EXERCISE_RESULTS_FILENAME || ''
+            results: process.env.EXERCISE_RESULTS_FILENAME ?? ''
         };
     }
 }
diff --git a/helpers/Dojo/AssignmentValidator.ts b/helpers/Dojo/AssignmentValidator.ts
index d35d8fc0932f3f1a923007ed1556e813a2f2cea1..a45d61d23f7f60ac7502523ae87994df47b23789 100644
--- a/helpers/Dojo/AssignmentValidator.ts
+++ b/helpers/Dojo/AssignmentValidator.ts
@@ -196,7 +196,7 @@ class AssignmentValidator {
                 });
 
                 dockerComposeValidation.on('exit', code => {
-                    code !== null && code === 0 ? resolve() : reject();
+                    code !== null && code === 0 ? resolve() : reject(code);
                 });
             });
         } catch ( error ) {
@@ -271,7 +271,7 @@ class AssignmentValidator {
                 });
 
                 exerciseDockerCompose.events.on('finished', (_success: boolean, exitCode: number) => {
-                    exitCode !== 0 ? resolve() : reject();
+                    exitCode !== 0 ? resolve() : reject(exitCode);
                 });
 
                 exerciseDockerCompose.run(this.doDown);
diff --git a/models/Exercise.ts b/models/Exercise.ts
index 710314ee1d377a117650fe1ced9ec171de104638..b8a2b83b02d763effa7516905028fd760da37cf7 100644
--- a/models/Exercise.ts
+++ b/models/Exercise.ts
@@ -1,5 +1,5 @@
 import GitlabRepository from '../../shared/types/Gitlab/GitlabRepository';
-import { CommitSchema } from '@gitbeaker/rest';
+import * as Gitlab      from '@gitbeaker/rest';
 import User             from './User';
 import Assignment       from './Assignment';
 
@@ -18,7 +18,7 @@ interface Exercise {
     assignment: Assignment | undefined;
 
     isCorrection: boolean;
-    correctionCommit: CommitSchema | undefined;
+    correctionCommit: Gitlab.CommitSchema | undefined;
 }