diff --git a/Source/WebCore/ChangeLog b/Source/WebCore/ChangeLog
index 981ae0b..e5d2029 100644
--- a/Source/WebCore/ChangeLog
+++ b/Source/WebCore/ChangeLog
@@ -1,3 +1,19 @@
+2021-10-13  Jean-Yves Avenard  <jya@apple.com>
+
+        Compilation error: error: definition of implicit copy assignment operator in AppHighlightRangeData.h
+        https://bugs.webkit.org/show_bug.cgi?id=231717
+        rdar://problem/84230745
+
+        Reviewed by Tim Horton.
+
+        Per C++11 and later:
+        “The generation of the implicitly-defined copy assignment operator is
+        deprecated if T has a user-declared destructor or user-declared copy
+        constructor.”
+        A copy constructor is defined, so we need to declare a copy assignement operator.
+
+        * Modules/highlight/AppHighlightRangeData.h: Add copy assignment operator.
+
 2021-10-13  Simon Fraser  <simon.fraser@apple.com>
 
         Use PlatformKeyboardEvent in KeyboardScrollingAnimator to fix a layering violation
diff --git a/Source/WebCore/Modules/highlight/AppHighlightRangeData.h b/Source/WebCore/Modules/highlight/AppHighlightRangeData.h
index f1fa524..cf6381a 100644
--- a/Source/WebCore/Modules/highlight/AppHighlightRangeData.h
+++ b/Source/WebCore/Modules/highlight/AppHighlightRangeData.h
@@ -99,6 +99,8 @@
     {
     }
 
+    AppHighlightRangeData& operator=(const AppHighlightRangeData&) = default;
+
     const String& identifier() const { return m_identifier; }
     const String& text() const { return m_text; }
     const NodePath& startContainer() const { return m_startContainer; }