diff --git a/Libraries/LibJS/Heap/Cell.h b/Libraries/LibJS/Heap/Cell.h
index 6fad37336b..0be2478583 100644
--- a/Libraries/LibJS/Heap/Cell.h
+++ b/Libraries/LibJS/Heap/Cell.h
@@ -17,7 +17,7 @@ class JS_API Cell : public GC::Cell {
     GC_CELL(Cell, GC::Cell);
 
 public:
-    virtual void initialize(Realm&);
+    MUST_UPCALL virtual void initialize(Realm&);
 
     virtual bool is_generator_result() const { return false; }
     virtual bool is_environment() const { return false; }
diff --git a/Libraries/LibJS/Runtime/Intl/CollatorCompareFunction.cpp b/Libraries/LibJS/Runtime/Intl/CollatorCompareFunction.cpp
index 94f682094f..cbc60350ce 100644
--- a/Libraries/LibJS/Runtime/Intl/CollatorCompareFunction.cpp
+++ b/Libraries/LibJS/Runtime/Intl/CollatorCompareFunction.cpp
@@ -24,8 +24,9 @@ CollatorCompareFunction::CollatorCompareFunction(Realm& realm, Collator& collato
 {
 }
 
-void CollatorCompareFunction::initialize(Realm&)
+void CollatorCompareFunction::initialize(Realm& realm)
 {
+    Base::initialize(realm);
     auto& vm = this->vm();
     define_direct_property(vm.names.length, Value(2), Attribute::Configurable);
     define_direct_property(vm.names.name, PrimitiveString::create(vm, String {}), Attribute::Configurable);
diff --git a/Libraries/LibJS/Runtime/Object.cpp b/Libraries/LibJS/Runtime/Object.cpp
index e9aae2bd0e..3a30403fe9 100644
--- a/Libraries/LibJS/Runtime/Object.cpp
+++ b/Libraries/LibJS/Runtime/Object.cpp
@@ -99,8 +99,9 @@ Object::~Object()
         s_intrinsics.remove(this);
 }
 
-void Object::initialize(Realm&)
+void Object::initialize(Realm& realm)
 {
+    Base::initialize(realm);
 }
 
 void Object::unsafe_set_shape(Shape& shape)
diff --git a/Libraries/LibJS/Runtime/Set.cpp b/Libraries/LibJS/Runtime/Set.cpp
index b0cbee89c2..aacb3bc4a2 100644
--- a/Libraries/LibJS/Runtime/Set.cpp
+++ b/Libraries/LibJS/Runtime/Set.cpp
@@ -24,6 +24,7 @@ Set::Set(Object& prototype)
 
 void Set::initialize(Realm& realm)
 {
+    Base::initialize(realm);
     m_values = Map::create(realm);
 }
 
diff --git a/Meta/Lagom/Tools/CodeGenerators/LibWeb/BindingsGenerator/IDLGenerators.cpp b/Meta/Lagom/Tools/CodeGenerators/LibWeb/BindingsGenerator/IDLGenerators.cpp
index 7a7beb78ec..ebfdfb1ed4 100644
--- a/Meta/Lagom/Tools/CodeGenerators/LibWeb/BindingsGenerator/IDLGenerators.cpp
+++ b/Meta/Lagom/Tools/CodeGenerators/LibWeb/BindingsGenerator/IDLGenerators.cpp
@@ -3487,6 +3487,7 @@ GC_DEFINE_ALLOCATOR(@named_properties_class@);
 
 void @named_properties_class@::initialize(JS::Realm& realm)
 {
+    Base::initialize(realm);
     auto& vm = realm.vm();
 
     // The class string of a named properties object is the concatenation of the interface's identifier and the string "Properties".