diff --git a/labs/behaviors/constraint-validation.ts b/labs/behaviors/constraint-validation.ts
index 748e27abad..897ffd6318 100644
--- a/labs/behaviors/constraint-validation.ts
+++ b/labs/behaviors/constraint-validation.ts
@@ -235,7 +235,7 @@ export function mixinConstraintValidation<
       const {validity, validationMessage: nonCustomValidationMessage} =
         this[privateValidator].getValidity();
 
-      const customError = !!this[privateCustomValidationMessage];
+      const customError = !!this[privateCustomValidationMessage] || validity.customError;
       const validationMessage =
         this[privateCustomValidationMessage] || nonCustomValidationMessage;
 
diff --git a/labs/behaviors/constraint-validation_test.ts b/labs/behaviors/constraint-validation_test.ts
index 5114070d6c..5e73a5460c 100644
--- a/labs/behaviors/constraint-validation_test.ts
+++ b/labs/behaviors/constraint-validation_test.ts
@@ -17,6 +17,8 @@ import {
 import {mixinElementInternals} from './element-internals.js';
 import {getFormValue, mixinFormAssociated} from './form-associated.js';
 import {CheckboxValidator} from './validators/checkbox-validator.js';
+import {Validator} from './validators/validator.js';
+import {SelectState} from './validators/select-validator.js';
 
 describe('mixinConstraintValidation()', () => {
   const baseClass = mixinConstraintValidation(
@@ -45,6 +47,52 @@ describe('mixinConstraintValidation()', () => {
     }
   }
 
+  /**
+   * A validator that set customError flag to true
+   */
+  class CustomErrorValidator extends Validator<SelectState> {
+    private control?: HTMLInputElement;
+
+    protected override computeValidity(state: SelectState) {
+      if (!this.control) {
+        this.control = document.createElement('input');
+      }
+      this.control.setCustomValidity('validator custom error');
+      return {
+        validity: this.control.validity,
+        validationMessage: this.control.validationMessage,
+      };
+    }
+
+    protected override equals(prev: SelectState, next: SelectState) {
+      return prev.value === next.value
+    }
+
+    protected override copy({ value, required }: SelectState) {
+      return { value, required };
+    }
+  }
+
+  @customElement('test-custom-error-constraint-validation')
+  class TestCustomErrorConstraintValidation extends baseClass {
+    @property() value = '';
+    @property({ type: Boolean }) required = false;
+    override render() {
+      return html`<div id="root"></div>`;
+    }
+    [createValidator]() {
+      return new CustomErrorValidator(() => this);
+    }
+
+    [getValidityAnchor]() {
+      return this.shadowRoot?.querySelector<HTMLElement>('#root') ?? null;
+    }
+
+    [getFormValue]() {
+      return String(this.value);
+    }
+  }
+
   describe('validity', () => {
     it('should return a ValidityState value', () => {
       const control = new TestConstraintValidation();
@@ -174,4 +222,26 @@ describe('mixinConstraintValidation()', () => {
         .toBe('Error');
     });
   });
+
+  describe('customError', () => {
+    it('should set customError to true when validator has customError', () => {
+      const control = new TestCustomErrorConstraintValidation();
+      expect(control.validity.customError)
+        .withContext('validity.customError')
+        .toBeTrue();
+    });
+    it('should dispatch invalid event when validator has customError', () => {
+      const control = new TestCustomErrorConstraintValidation();
+      const invalidListener = jasmine.createSpy('invalidListener');
+      control.addEventListener('invalid', invalidListener);
+      control.reportValidity();
+      expect(invalidListener).toHaveBeenCalledWith(jasmine.any(Event));
+    });
+    it('should report custom validation message over other validation messages', () => {
+      const control = new TestCustomErrorConstraintValidation();
+      expect(control.validationMessage)
+        .withContext('validationMessage')
+        .toBe('validator custom error');
+    });
+  })
 });