diff --git a/fxjs/gc/gced_tree_node_embeddertest.cpp b/fxjs/gc/gced_tree_node_embeddertest.cpp
index 25a25b3..cbda307 100644
--- a/fxjs/gc/gced_tree_node_embeddertest.cpp
+++ b/fxjs/gc/gced_tree_node_embeddertest.cpp
@@ -4,6 +4,8 @@
 
 #include "fxjs/gc/gced_tree_node.h"
 
+#include <map>
+
 #include "core/fxcrt/observed_ptr.h"
 #include "fxjs/gc/heap.h"
 #include "testing/gced_embeddertest.h"
@@ -144,3 +146,10 @@
   EXPECT_TRUE(s_root);
   EXPECT_FALSE(watcher);
 }
+
+TEST_F(GCedTreeNodeEmbedderTest, AsMapKey) {
+  std::map<cppgc::Persistent<ObservableGCedTreeNodeForTest>, int> score;
+  ObservableGCedTreeNodeForTest* node = CreateNode();
+  score[node] = 100;
+  EXPECT_EQ(100, score[node]);
+}