diff --git a/packages/fieldset/test/lion-fieldset.test.js b/packages/fieldset/test/lion-fieldset.test.js
index d9f003ad4..88521726f 100644
--- a/packages/fieldset/test/lion-fieldset.test.js
+++ b/packages/fieldset/test/lion-fieldset.test.js
@@ -9,8 +9,6 @@ import {
 } from '@open-wc/testing';
 import sinon from 'sinon';
 import { localizeTearDown } from '@lion/localize/test-helpers.js';
-import '@lion/input/lion-input.js';
-
 import '../lion-fieldset.js';
 
 const tagString = 'lion-fieldset';
@@ -293,6 +291,38 @@ describe('<lion-fieldset>', () => {
       el.formElements.color.modelValue = 'cat';
       expect(el.error).to.deep.equal({});
     });
+
+    it('validates on children (de)registration', async () => {
+      function hasEvenNumberOfChildren(modelValue) {
+        return { even: Object.keys(modelValue).length % 2 === 0 };
+      }
+      const el = await fixture(html`
+        <${tag} .errorValidators=${[[hasEvenNumberOfChildren]]}>
+          <lion-input id="c1" name="c1"></lion-input>
+        </${tag}>
+      `);
+      const child2 = await fixture(
+        html`
+          <lion-input name="c2"></lion-input>
+        `,
+      );
+
+      await nextFrame();
+      expect(el.error.even).to.equal(true);
+
+      el.appendChild(child2);
+      await nextFrame();
+      expect(el.error.even).to.equal(undefined);
+
+      el.removeChild(child2);
+      await nextFrame();
+      expect(el.error.even).to.equal(true);
+
+      // Edge case: remove all children
+      el.removeChild(el.querySelector('[id=c1]'));
+      await nextFrame();
+      expect(el.error.even).to.equal(undefined);
+    });
   });
 
   describe('interaction states', () => {
diff --git a/packages/validate/src/ValidateMixin.js b/packages/validate/src/ValidateMixin.js
index d0d1d7059..0de305129 100644
--- a/packages/validate/src/ValidateMixin.js
+++ b/packages/validate/src/ValidateMixin.js
@@ -385,7 +385,10 @@ export const ValidateMixin = dedupeMixin(
        * Other transitions (from Warning/Info) are not followed by a success message
        */
       validate() {
-        if (this.modelValue === undefined) return;
+        if (this.modelValue === undefined) {
+          this.__resetValidationStates();
+          return;
+        }
         this.__oldValidationStates = this.getValidationStates();
         this.constructor.validationTypes.forEach(type => {
           this.validateType(type);
@@ -393,6 +396,13 @@ export const ValidateMixin = dedupeMixin(
         this.dispatchEvent(new CustomEvent('validation-done', { bubbles: true, composed: true }));
       }
 
+      __resetValidationStates() {
+        this.constructor.validationTypes.forEach(type => {
+          this[`${type}State`] = false;
+          this[type] = {};
+        });
+      }
+
       /**
        * Override if needed
        */
diff --git a/packages/validate/test/ValidateMixin.test.js b/packages/validate/test/ValidateMixin.test.js
index 1324c350c..99dd36d44 100644
--- a/packages/validate/test/ValidateMixin.test.js
+++ b/packages/validate/test/ValidateMixin.test.js
@@ -501,6 +501,37 @@ describe('ValidateMixin', () => {
       expect(cbInfo.callCount).to.equal(2);
       expect(cbSuccess.callCount).to.equal(1);
     });
+
+    it('removes invalid states whenever modelValue becomes undefined', async () => {
+      const el = await fixture(html`
+        <${tag}
+          .errorValidators=${[[minLength, { min: 3 }]]}
+          .warningValidators=${[[minLength, { min: 5 }]]}
+          .infoValidators=${[[minLength, { min: 7 }]]}
+          .successValidators=${[[alwaysFalse]]}
+        >${lightDom}</${tag}>
+      `);
+
+      el.modelValue = 'a';
+      expect(el.errorState).to.equal(true);
+      expect(el.warningState).to.equal(true);
+      expect(el.infoState).to.equal(true);
+      expect(el.successState).to.equal(true);
+      expect(el.error).to.not.eql({});
+      expect(el.warning).to.not.eql({});
+      expect(el.info).to.not.eql({});
+      expect(el.success).to.not.eql({});
+
+      el.modelValue = undefined;
+      expect(el.errorState).to.equal(false);
+      expect(el.warningState).to.equal(false);
+      expect(el.infoState).to.equal(false);
+      expect(el.successState).to.equal(false);
+      expect(el.error).to.eql({});
+      expect(el.warning).to.eql({});
+      expect(el.info).to.eql({});
+      expect(el.success).to.eql({});
+    });
   });
 
   describe(`Accessibility ${suffixName}`, () => {
@@ -690,6 +721,9 @@ describe('ValidateMixin', () => {
       const errorRenderer = defineCE(
         class extends HTMLElement {
           renderFeedback(validationStates, message) {
+            if (!message.list.length) {
+              return;
+            }
             const validator = message.list[0].data.validatorName;
             const showError = validationStates.error;
             this.innerText = showError ? `ERROR on ${validator}` : '';
@@ -982,6 +1016,9 @@ describe('ValidateMixin', () => {
         const errorRenderer = defineCE(
           class extends HTMLElement {
             renderFeedback(validationStates, message) {
+              if (!message.list.length) {
+                return;
+              }
               const validator = message.list[0].data.validatorName;
               const hide =
                 message.list[0].data.validatorConfig &&