--- a/js/src/jsapi.cpp
+++ b/js/src/jsapi.cpp
@@ -1573,16 +1573,23 @@ JS::RealmCreationOptions::setNewCompartm
 
 JS::RealmCreationOptions& JS::RealmCreationOptions::setExistingCompartment(
     JSObject* obj) {
   compSpec_ = CompartmentSpecifier::ExistingCompartment;
   comp_ = obj->compartment();
   return *this;
 }
 
+JS::RealmCreationOptions& JS::RealmCreationOptions::setExistingCompartment(
+    JS::Compartment* compartment) {
+  compSpec_ = CompartmentSpecifier::ExistingCompartment;
+  comp_ = compartment;
+  return *this;
+}
+
 JS::RealmCreationOptions& JS::RealmCreationOptions::setNewCompartmentAndZone() {
   compSpec_ = CompartmentSpecifier::NewCompartmentAndZone;
   comp_ = nullptr;
   return *this;
 }
 
 const JS::RealmCreationOptions& JS::RealmCreationOptionsRef(Realm* realm) {
   return realm->creationOptions();

--- a/js/src/jsapi.h
+++ b/js/src/jsapi.h
@@ -967,16 +967,17 @@ class JS_PUBLIC_API RealmCreationOptions
   CompartmentSpecifier compartmentSpecifier() const { return compSpec_; }
 
   // Set the compartment/zone to use for the realm. See CompartmentSpecifier
   // above.
   RealmCreationOptions& setNewCompartmentInSystemZone();
   RealmCreationOptions& setNewCompartmentInExistingZone(JSObject* obj);
   RealmCreationOptions& setNewCompartmentAndZone();
   RealmCreationOptions& setExistingCompartment(JSObject* obj);
+  RealmCreationOptions& setExistingCompartment(JS::Compartment* compartment);
 
   // Certain compartments are implementation details of the embedding, and
   // references to them should never leak out to script. This flag causes this
   // realm to skip firing onNewGlobalObject and makes addDebuggee a no-op for
   // this global.
   //
   // Debugger visibility is per-compartment, not per-realm (it's only practical
   // to enforce visibility on compartment boundaries), so if a realm is being