diff --git a/packages/time-picker/src/vaadin-time-picker.js b/packages/time-picker/src/vaadin-time-picker.js
index 72dbf0fd97..1cf097498d 100644
--- a/packages/time-picker/src/vaadin-time-picker.js
+++ b/packages/time-picker/src/vaadin-time-picker.js
@@ -323,7 +323,7 @@ class TimePicker extends PatternMixin(InputControlMixin(ThemableMixin(ElementMix
   static get observers() {
     return [
       '__updateAriaAttributes(__dropdownItems, opened, inputElement)',
-      '__updateDropdownItems(i18n.*, min, max, step)',
+      '__updateDropdownItems(i18n, min, max, step)',
     ];
   }
 
@@ -589,7 +589,7 @@ class TimePicker extends PatternMixin(InputControlMixin(ThemableMixin(ElementMix
   }
 
   /** @private */
-  __updateDropdownItems(_i18n, min, max, step) {
+  __updateDropdownItems(i18n, min, max, step) {
     const minTimeObj = validateTime(parseISOTime(min || MIN_ALLOWED_TIME), step);
     const minSec = this.__getSec(minTimeObj);
 
@@ -605,7 +605,7 @@ class TimePicker extends PatternMixin(InputControlMixin(ThemableMixin(ElementMix
     }
 
     if (this.value) {
-      this._comboBoxValue = this.i18n.formatTime(this.i18n.parseTime(this.value));
+      this._comboBoxValue = i18n.formatTime(i18n.parseTime(this.value));
     }
   }
 
diff --git a/packages/time-picker/test/time-picker.test.js b/packages/time-picker/test/time-picker.test.js
index 1a39fd234f..fde2be6ef4 100644
--- a/packages/time-picker/test/time-picker.test.js
+++ b/packages/time-picker/test/time-picker.test.js
@@ -391,7 +391,7 @@ describe('time-picker', () => {
 
   describe('custom functions', () => {
     it('should use custom parser if that exists', () => {
-      timePicker.set('i18n.parseTime', sinon.stub().returns({ hours: 12, minutes: 0, seconds: 0 }));
+      timePicker.i18n = { ...timePicker.i18n, parseTime: sinon.stub().returns({ hours: 12, minutes: 0, seconds: 0 }) };
       timePicker.value = '12';
       expect(timePicker.i18n.parseTime.args[0][0]).to.be.equal('12:00');
       expect(timePicker.value).to.be.equal('12:00');
@@ -399,10 +399,10 @@ describe('time-picker', () => {
 
     it('should align values of dropdown and input when i18n was reassigned', () => {
       timePicker.value = '12';
-      timePicker.set('i18n', {
+      timePicker.i18n = {
         formatTime: sinon.stub().withArgs({ hours: 12, minutes: 0 }).returns('12:00 AM'),
         parseTime: sinon.stub().returns({ hours: 12, minutes: 0, seconds: 0 }),
-      });
+      };
       expect(comboBox.selectedItem).to.be.deep.equal({ label: '12:00 AM', value: '12:00 AM' });
       expect(comboBox.value).to.be.equal('12:00 AM');
       expect(inputElement.value).to.be.equal('12:00 AM');
@@ -410,20 +410,20 @@ describe('time-picker', () => {
     });
 
     it('should use custom formatter if that exists', () => {
-      timePicker.set('i18n', {
+      timePicker.i18n = {
         formatTime: sinon.stub().withArgs({ hours: 12, minutes: 0 }).returns('12:00 AM'),
         parseTime: sinon.stub().returns({ hours: 12, minutes: 0, seconds: 0 }),
-      });
+      };
       timePicker.value = '12';
       expect(timePicker.value).to.be.equal('12:00');
       expect(comboBox.value).to.be.equal('12:00 AM');
     });
 
     it('should accept custom time formatter', () => {
-      timePicker.set('i18n.formatTime', sinon.stub().returns('1200'));
-      const parseTime = sinon.stub();
-      parseTime.withArgs('1200').returns({ hours: 12, minutes: 0 });
-      timePicker.set('i18n.parseTime', parseTime);
+      timePicker.i18n = {
+        formatTime: sinon.stub().returns('1200'),
+        parseTime: sinon.stub().withArgs('1200').returns({ hours: 12, minutes: 0 }),
+      };
       timePicker.value = '12:00';
       expect(inputElement.value).to.equal('1200');
       expect(timePicker.value).to.equal('12:00');