diff --git a/Libraries/LibJS/Bytecode/ASTCodegen.cpp b/Libraries/LibJS/Bytecode/ASTCodegen.cpp
index 13732eef188..14ab23641be 100644
--- a/Libraries/LibJS/Bytecode/ASTCodegen.cpp
+++ b/Libraries/LibJS/Bytecode/ASTCodegen.cpp
@@ -630,6 +630,13 @@ Bytecode::CodeGenerationErrorOr<Optional<ScopedOperand>> AssignmentExpression::g
                 // e. Perform ? PutValue(lref, rval).
                 if (is<Identifier>(*lhs)) {
                     auto& identifier = static_cast<Identifier const&>(*lhs);
+                    if (identifier.is_local()) {
+                        auto is_initialized = generator.is_local_initialized(identifier.local_index());
+                        auto is_lexically_declared = generator.is_local_lexically_declared(identifier.local_index());
+                        if (is_lexically_declared && !is_initialized) {
+                            generator.emit<Bytecode::Op::ThrowIfTDZ>(generator.local(identifier.local_index()));
+                        }
+                    }
                     generator.emit_set_variable(identifier, rval);
                 } else if (is<MemberExpression>(*lhs)) {
                     auto& expression = static_cast<MemberExpression const&>(*lhs);
diff --git a/Tests/LibWeb/Text/input/WebAnimations/animation-methods/persist.html b/Tests/LibWeb/Text/input/WebAnimations/animation-methods/persist.html
index 372fb4ad7cb..c1b0c3f63b0 100644
--- a/Tests/LibWeb/Text/input/WebAnimations/animation-methods/persist.html
+++ b/Tests/LibWeb/Text/input/WebAnimations/animation-methods/persist.html
@@ -13,15 +13,15 @@
         anim.cancel();
 
         // "Undo" the removal of an animation by the Document
-        anim1 = foo.animate({ opacity: 0 }, { duration: 1, fill: 'forwards' });
-        anim2 = foo.animate({ opacity: 0 }, { duration: 1, fill: 'forwards' });
+        let anim1 = foo.animate({ opacity: 0 }, { duration: 1, fill: 'forwards' });
+        let anim2 = foo.animate({ opacity: 0 }, { duration: 1, fill: 'forwards' });
         await anim1.finished;
         anim1.persist();
         println(`persist() undoes the Document removal effects: ${foo.getAnimations().length === 2}`);
 
         const timeline = internals.createInternalAnimationTimeline();
-        let anim1 = foo.animate({ opacity: 0 }, { duration: 1000, fill: "forwards", timeline });
-        let anim2 = foo.animate({ opacity: 0 }, { duration: 500, fill: "forwards", timeline });
+        anim1 = foo.animate({ opacity: 0 }, { duration: 1000, fill: "forwards", timeline });
+        anim2 = foo.animate({ opacity: 0 }, { duration: 500, fill: "forwards", timeline });
         timeline.setTime(1500);
         await animationFrame();
         if (anim1.replaceState === "removed" && anim2.replaceState === "active")