diff --git a/libs/ftl/small_map_test.cpp b/libs/ftl/small_map_test.cpp
index c292108..ee650e5 100644
--- a/libs/ftl/small_map_test.cpp
+++ b/libs/ftl/small_map_test.cpp
@@ -362,4 +362,24 @@
   EXPECT_TRUE(map.dynamic());
 }
 
+TEST(SmallMap, KeyEqual) {
+  struct KeyEqual {
+    bool operator()(int lhs, int rhs) const { return lhs % 10 == rhs % 10; }
+  };
+
+  SmallMap<int, char, 1, KeyEqual> map;
+
+  EXPECT_TRUE(map.try_emplace(3, '3').second);
+  EXPECT_FALSE(map.try_emplace(13, '3').second);
+
+  EXPECT_TRUE(map.try_emplace(22, '2').second);
+  EXPECT_TRUE(map.contains(42));
+
+  EXPECT_TRUE(map.try_emplace(111, '1').second);
+  EXPECT_EQ(map.get(321), '1');
+
+  map.erase(123);
+  EXPECT_EQ(map, SmallMap(ftl::init::map<int, char, KeyEqual>(1, '1')(2, '2')));
+}
+
 }  // namespace android::test