diff --git a/Userland/Libraries/LibWeb/CodeGenerators/WrapperGenerator.cpp b/Userland/Libraries/LibWeb/CodeGenerators/WrapperGenerator.cpp
index bfe1182aff..8de7548a58 100644
--- a/Userland/Libraries/LibWeb/CodeGenerators/WrapperGenerator.cpp
+++ b/Userland/Libraries/LibWeb/CodeGenerators/WrapperGenerator.cpp
@@ -573,7 +573,8 @@ static void generate_to_cpp(SourceGenerator& generator, ParameterType& parameter
 )~~~");
         }
     } else if (is_wrappable_type(parameter.type)) {
-        scoped_generator.append(R"~~~(
+        if (!parameter.type.nullable) {
+            scoped_generator.append(R"~~~(
     auto @cpp_name@_object = @js_name@@js_suffix@.to_object(global_object);
     if (vm.exception())
         @return_statement@
@@ -585,6 +586,23 @@ static void generate_to_cpp(SourceGenerator& generator, ParameterType& parameter
 
     auto& @cpp_name@ = static_cast<@parameter.type.name@Wrapper*>(@cpp_name@_object)->impl();
 )~~~");
+        } else {
+            scoped_generator.append(R"~~~(
+    @parameter.type.name@* @cpp_name@ = nullptr;
+    if (!@js_name@@js_suffix@.is_null()) {
+        auto @cpp_name@_object = @js_name@@js_suffix@.to_object(global_object);
+        if (vm.exception())
+            @return_statement@
+
+        if (!is<@parameter.type.name@Wrapper>(@cpp_name@_object)) {
+            vm.throw_exception<JS::TypeError>(global_object, JS::ErrorType::NotA, "@parameter.type.name@");
+            @return_statement@
+        }
+
+        @cpp_name@ = &static_cast<@parameter.type.name@Wrapper*>(@cpp_name@_object)->impl();
+    }
+)~~~");
+        }
     } else if (parameter.type.name == "double") {
         if (!optional) {
             scoped_generator.append(R"~~~(
diff --git a/Userland/Libraries/LibWeb/DOM/Document.cpp b/Userland/Libraries/LibWeb/DOM/Document.cpp
index 2d6ade6c5d..62871e8630 100644
--- a/Userland/Libraries/LibWeb/DOM/Document.cpp
+++ b/Userland/Libraries/LibWeb/DOM/Document.cpp
@@ -215,14 +215,14 @@ HTML::HTMLElement* Document::body()
 }
 
 // https://html.spec.whatwg.org/multipage/dom.html#dom-document-body
-ExceptionOr<void> Document::set_body(HTML::HTMLElement& new_body)
+ExceptionOr<void> Document::set_body(HTML::HTMLElement* new_body)
 {
     if (!is<HTML::HTMLBodyElement>(new_body) && !is<HTML::HTMLFrameSetElement>(new_body))
         return DOM::HierarchyRequestError::create("Invalid document body element, must be 'body' or 'frameset'");
 
     auto* existing_body = body();
     if (existing_body) {
-        auto replace_result = existing_body->parent()->replace_child(new_body, *existing_body);
+        auto replace_result = existing_body->parent()->replace_child(*new_body, *existing_body);
         if (replace_result.is_exception())
             return replace_result.exception();
         return {};
@@ -232,7 +232,7 @@ ExceptionOr<void> Document::set_body(HTML::HTMLElement& new_body)
     if (!document_element)
         return DOM::HierarchyRequestError::create("Missing document element");
 
-    auto append_result = document_element->append_child(new_body);
+    auto append_result = document_element->append_child(*new_body);
     if (append_result.is_exception())
         return append_result.exception();
     return {};
diff --git a/Userland/Libraries/LibWeb/DOM/Document.h b/Userland/Libraries/LibWeb/DOM/Document.h
index 0d9a999d1c..4225636f73 100644
--- a/Userland/Libraries/LibWeb/DOM/Document.h
+++ b/Userland/Libraries/LibWeb/DOM/Document.h
@@ -110,7 +110,7 @@ public:
         return const_cast<Document*>(this)->body();
     }
 
-    ExceptionOr<void> set_body(HTML::HTMLElement& new_body);
+    ExceptionOr<void> set_body(HTML::HTMLElement* new_body);
 
     String title() const;
     void set_title(const String&);
diff --git a/Userland/Libraries/LibWeb/HTML/HTMLTableElement.cpp b/Userland/Libraries/LibWeb/HTML/HTMLTableElement.cpp
index 16e44a3078..bb23a9882c 100644
--- a/Userland/Libraries/LibWeb/HTML/HTMLTableElement.cpp
+++ b/Userland/Libraries/LibWeb/HTML/HTMLTableElement.cpp
@@ -51,13 +51,16 @@ RefPtr<HTMLTableCaptionElement> HTMLTableElement::caption()
     return first_child_of_type<HTMLTableCaptionElement>();
 }
 
-void HTMLTableElement::set_caption(HTMLTableCaptionElement& caption)
+void HTMLTableElement::set_caption(HTMLTableCaptionElement* caption)
 {
+    // FIXME: This is not always the case, but this function is currently written in a way that assumes non-null.
+    VERIFY(caption);
+
     // FIXME: The spec requires deleting the current caption if caption is null
     //        Currently the wrapper generator doesn't send us a nullable value
     delete_caption();
 
-    pre_insert(caption, first_child());
+    pre_insert(*caption, first_child());
 }
 
 NonnullRefPtr<HTMLTableCaptionElement> HTMLTableElement::create_caption()
@@ -93,9 +96,12 @@ RefPtr<HTMLTableSectionElement> HTMLTableElement::t_head()
     return nullptr;
 }
 
-DOM::ExceptionOr<void> HTMLTableElement::set_t_head(HTMLTableSectionElement& thead)
+DOM::ExceptionOr<void> HTMLTableElement::set_t_head(HTMLTableSectionElement* thead)
 {
-    if (thead.tag_name() != TagNames::thead)
+    // FIXME: This is not always the case, but this function is currently written in a way that assumes non-null.
+    VERIFY(thead);
+
+    if (thead->tag_name() != TagNames::thead)
         return DOM::HierarchyRequestError::create("Element is not thead");
 
     // FIXME: The spec requires deleting the current thead if thead is null
@@ -120,7 +126,7 @@ DOM::ExceptionOr<void> HTMLTableElement::set_t_head(HTMLTableSectionElement& the
         break;
     }
 
-    pre_insert(thead, child_to_append_after);
+    pre_insert(*thead, child_to_append_after);
 
     return {};
 }
@@ -177,9 +183,12 @@ RefPtr<HTMLTableSectionElement> HTMLTableElement::t_foot()
     return nullptr;
 }
 
-DOM::ExceptionOr<void> HTMLTableElement::set_t_foot(HTMLTableSectionElement& tfoot)
+DOM::ExceptionOr<void> HTMLTableElement::set_t_foot(HTMLTableSectionElement* tfoot)
 {
-    if (tfoot.tag_name() != TagNames::tfoot)
+    // FIXME: This is not always the case, but this function is currently written in a way that assumes non-null.
+    VERIFY(tfoot);
+
+    if (tfoot->tag_name() != TagNames::tfoot)
         return DOM::HierarchyRequestError::create("Element is not tfoot");
 
     // FIXME: The spec requires deleting the current tfoot if tfoot is null
@@ -187,7 +196,7 @@ DOM::ExceptionOr<void> HTMLTableElement::set_t_foot(HTMLTableSectionElement& tfo
     delete_t_foot();
 
     // We insert the new tfoot at the end of the table
-    append_child(tfoot);
+    append_child(*tfoot);
 
     return {};
 }
diff --git a/Userland/Libraries/LibWeb/HTML/HTMLTableElement.h b/Userland/Libraries/LibWeb/HTML/HTMLTableElement.h
index 6565017d2d..a91a1af20a 100644
--- a/Userland/Libraries/LibWeb/HTML/HTMLTableElement.h
+++ b/Userland/Libraries/LibWeb/HTML/HTMLTableElement.h
@@ -22,17 +22,17 @@ public:
     virtual ~HTMLTableElement() override;
 
     RefPtr<HTMLTableCaptionElement> caption();
-    void set_caption(HTMLTableCaptionElement&);
+    void set_caption(HTMLTableCaptionElement*);
     NonnullRefPtr<HTMLTableCaptionElement> create_caption();
     void delete_caption();
 
     RefPtr<HTMLTableSectionElement> t_head();
-    DOM::ExceptionOr<void> set_t_head(HTMLTableSectionElement& thead);
+    DOM::ExceptionOr<void> set_t_head(HTMLTableSectionElement* thead);
     NonnullRefPtr<HTMLTableSectionElement> create_t_head();
     void delete_t_head();
 
     RefPtr<HTMLTableSectionElement> t_foot();
-    DOM::ExceptionOr<void> set_t_foot(HTMLTableSectionElement& thead);
+    DOM::ExceptionOr<void> set_t_foot(HTMLTableSectionElement* tfoot);
     NonnullRefPtr<HTMLTableSectionElement> create_t_foot();
     void delete_t_foot();