diff --git a/frontend/CHANGELOG.md b/frontend/CHANGELOG.md
index 84dc7d2..b56dc01 100644
--- a/frontend/CHANGELOG.md
+++ b/frontend/CHANGELOG.md
@@ -4,6 +4,7 @@
 
 - feature: multi select for organisations
 - bugfix: allow multiple query parameters to be set
+- bugfix: select check all methods could return 0 instead of a boolean
 - chore: bump @angular-eslint/eslint-plugin to 18.3.1
 - chore: bump typescript-eslint to 8.6.0
 - chore: bump @typescript/eslint-plugin to 8.14.0
diff --git a/frontend/src/app/core/components/select-check-all.component.spec.ts b/frontend/src/app/core/components/select-check-all.component.spec.ts
new file mode 100644
index 0000000..4f46d23
--- /dev/null
+++ b/frontend/src/app/core/components/select-check-all.component.spec.ts
@@ -0,0 +1,30 @@
+import { ComponentFixture, TestBed } from '@angular/core/testing';
+import { SelectCheckAllComponent } from './select-check-all.component';
+import { FormControl } from '@angular/forms';
+
+describe('SelectCheckAll', () => {
+  let fixture: ComponentFixture<SelectCheckAllComponent>;
+  let sut: SelectCheckAllComponent;
+
+  beforeEach(async () => {
+    TestBed.configureTestingModule({
+      imports: [SelectCheckAllComponent],
+      providers: [],
+    }).compileComponents();
+
+    fixture = TestBed.createComponent(SelectCheckAllComponent);
+    sut = fixture.componentInstance;
+    sut.model = new FormControl([]);
+    sut.values = [];
+    sut.text = 'Alle';
+  });
+  it('component loaded', () => {
+    expect(sut).not.toBeNull();
+  });
+  it('is not checked', () => {
+    expect(sut.isChecked()).toBe(false);
+  });
+  it('is not indeterminate', () => {
+    expect(sut.isIndeterminate()).toBe(false);
+  });
+});
diff --git a/frontend/src/app/core/components/select-check-all.component.ts b/frontend/src/app/core/components/select-check-all.component.ts
index e8540ff..7b53fb0 100644
--- a/frontend/src/app/core/components/select-check-all.component.ts
+++ b/frontend/src/app/core/components/select-check-all.component.ts
@@ -30,19 +30,19 @@ export class SelectCheckAllComponent {
   @Output() changeEvent = new EventEmitter<boolean>();
 
   isChecked(): boolean {
-    return (
+    return Boolean(
       this.model.value &&
-      this.values.length &&
-      this.model.value.length === this.values.length
+        this.values.length &&
+        this.model.value.length === this.values.length
     );
   }
 
   isIndeterminate(): boolean {
-    return (
+    return Boolean(
       this.model.value &&
-      this.values.length &&
-      this.model.value.length &&
-      this.model.value.length < this.values.length
+        this.values.length &&
+        this.model.value.length &&
+        this.model.value.length < this.values.length
     );
   }