diff --git a/CMakeLists.txt b/CMakeLists.txt
index 0925fdc..918306d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -47,7 +47,7 @@ if(WIN32)
   target_sources(kabufuda PRIVATE
     lib/kabufuda/AsyncIOWin32.cpp
   )
-elseif(NX)
+elseif(NX OR EMSCRIPTEN)
   target_sources(kabufuda PRIVATE
     lib/kabufuda/AsyncIONX.cpp
   )
diff --git a/include/kabufuda/AsyncIO.hpp b/include/kabufuda/AsyncIO.hpp
index 242dcb3..6a3f227 100644
--- a/include/kabufuda/AsyncIO.hpp
+++ b/include/kabufuda/AsyncIO.hpp
@@ -23,7 +23,7 @@ struct AsyncIOInner;
 #endif
 
 class AsyncIO {
-#ifdef __SWITCH__
+#if defined(__SWITCH__) || defined(EMSCRIPTEN)
   FILE* m_fd;
 #elif !defined(_WIN32)
   int m_fd = -1;
@@ -48,7 +48,7 @@ public:
   ECardResult pollStatus(size_t qIdx, SizeReturn* szRet = nullptr) const;
   ECardResult pollStatus() const;
   void waitForCompletion() const;
-#ifdef __SWITCH__
+#if defined(__SWITCH__) || defined(EMSCRIPTEN)
   explicit operator bool() const { return m_fd != nullptr; }
 #elif !defined(_WIN32)
   explicit operator bool() const { return m_fd != -1; }