diff --git a/client/src/app/core/ui-services/theme.service.ts b/client/src/app/core/ui-services/theme.service.ts
index cf75f4588..a92de283e 100644
--- a/client/src/app/core/ui-services/theme.service.ts
+++ b/client/src/app/core/ui-services/theme.service.ts
@@ -41,17 +41,26 @@ export class ThemeService {
             if (!newTheme) {
                 return;
             }
-            this.currentTheme = newTheme;
-
-            const classList = document.getElementsByTagName('body')[0].classList; // Get the classlist of the body.
-            const toRemove = Array.from(classList).filter((item: string) => item.includes('theme'));
-            if (toRemove.length) {
-                classList.remove(...toRemove); // Remove all old themes.
-            }
-            classList.add(newTheme, ThemeService.DEFAULT_THEME); // Add the new theme.
+            this.changeTheme(newTheme);
         });
     }
 
+    /**
+     * Function to change the theme and ensures, that old themes are removed.
+     *
+     * @param theme The theme which is applied.
+     */
+    private changeTheme(theme: string): void {
+        this.currentTheme = theme;
+
+        const classList = document.getElementsByTagName('body')[0].classList; // Get the classlist of the body.
+        const toRemove = Array.from(classList).filter((item: string) => item.includes('theme'));
+        if (toRemove.length) {
+            classList.remove(...toRemove); // Remove all old themes.
+        }
+        classList.add(theme, ThemeService.DEFAULT_THEME); // Add the new theme.
+    }
+
     /**
      * Returns the logo relative to the used theme.
      *
@@ -68,4 +77,17 @@ export class ThemeService {
             return null;
         }
     }
+
+    /**
+     * Function to ensure, that there is at least one theme set to define
+     * the colors of the components.
+     *
+     * If a theme is already set, nothing happens, otherwise the
+     * `DEFAULT_THEME` will be set.
+     */
+    public checkTheme(): void {
+        if (!this.currentTheme || this.currentTheme === '') {
+            this.changeTheme(ThemeService.DEFAULT_THEME);
+        }
+    }
 }
diff --git a/client/src/app/site/login/components/reset-password/reset-password.component.ts b/client/src/app/site/login/components/reset-password/reset-password.component.ts
index d04ef0c44..cb6c5f3a8 100644
--- a/client/src/app/site/login/components/reset-password/reset-password.component.ts
+++ b/client/src/app/site/login/components/reset-password/reset-password.component.ts
@@ -9,6 +9,7 @@ import { TranslateService } from '@ngx-translate/core';
 import { environment } from 'environments/environment';
 import { BaseComponent } from '../../../../base.component';
 import { HttpService } from 'app/core/core-services/http.service';
+import { ThemeService } from 'app/core/ui-services/theme.service';
 
 /**
  * Reset password component.
@@ -34,7 +35,8 @@ export class ResetPasswordComponent extends BaseComponent implements OnInit {
         private http: HttpService,
         formBuilder: FormBuilder,
         private matSnackBar: MatSnackBar,
-        private router: Router
+        private router: Router,
+        private themeService: ThemeService
     ) {
         super(titleService, translate);
         this.resetPasswordForm = formBuilder.group({
@@ -47,6 +49,7 @@ export class ResetPasswordComponent extends BaseComponent implements OnInit {
      */
     public ngOnInit(): void {
         super.setTitle('Reset password');
+        this.themeService.checkTheme();
     }
 
     /**