diff --git a/components/js_injection/renderer/js_binding.cc b/components/js_injection/renderer/js_binding.cc
index d93325c2a6f01..b115673a6330d 100644
--- a/components/js_injection/renderer/js_binding.cc
+++ b/components/js_injection/renderer/js_binding.cc
@@ -113,6 +113,14 @@ cppgc::WeakPersistent<JsBinding> JsBinding::Install(
       return nullptr;
     }
 
+    context_scope.emplace(context);
+  } else if (!context.IsEmpty() && context != isolate->GetCurrentContext()) {
+    // The caller pre-entered a (main-world) Context::Scope as an
+    // optimisation, but `context` may be a different (isolated) world.
+    // gin::WrappableBase::GetWrapper() instantiates the wrapper in
+    // isolate->GetCurrentContext(), so without this scope the wrapper's
+    // prototype chain would terminate at the *main-world* Object.prototype,
+    // letting page script poison it and capture this object.
     context_scope.emplace(context);
   }
   JsBinding* js_binding = cppgc::MakeGarbageCollected<JsBinding>(