diff --git a/src/__tests__/store.js b/src/__tests__/store.js
index 6bec1ce29..eeef8f807 100644
--- a/src/__tests__/store.js
+++ b/src/__tests__/store.js
@@ -81,8 +81,8 @@ describe('Store', () => {
   test('should default highlighting tags should be undefined', () => {
     const store = createStore();
 
-    expect(store.highlightPreTag).toEqual(undefined);
-    expect(store.highlightPostTag).toEqual(undefined);
+    expect(store.highlightPreTag).toEqual('<em>');
+    expect(store.highlightPostTag).toEqual('</em>');
   });
 
   test('can retrieve index name', () => {
@@ -346,8 +346,8 @@ describe('Store', () => {
 
     expect(store.queryParameters).toEqual(
       expect.objectContaining({
-        highlightPreTag: undefined,
-        highlightPostTag: undefined,
+        highlightPreTag: '<em>',
+        highlightPostTag: '</em>',
       })
     );
   });
diff --git a/src/store.js b/src/store.js
index bb0d450de..5ebed9d44 100644
--- a/src/store.js
+++ b/src/store.js
@@ -50,8 +50,8 @@ export class Store {
     // without trigger multiple queries.
     this._stoppedCounter = 1;
 
-    this._highlightPreTag = undefined;
-    this._highlightPostTag = undefined;
+    this._highlightPreTag = '<em>';
+    this._highlightPostTag = '</em>';
 
     this._cacheEnabled = true;