diff --git a/asio/include/asio/detail/impl/descriptor_ops.ipp b/asio/include/asio/detail/impl/descriptor_ops.ipp
index 9e88ab502d..0122027151 100644
--- a/asio/include/asio/detail/impl/descriptor_ops.ipp
+++ b/asio/include/asio/detail/impl/descriptor_ops.ipp
@@ -57,14 +57,14 @@ int close(int d, state_type& state, asio::error_code& ec)
       // current OS where this behaviour is seen, Windows, says that the socket
       // remains open. Therefore we'll put the descriptor back into blocking
       // mode and have another attempt at closing it.
-#if defined(__SYMBIAN32__)
+#if defined(__SYMBIAN32__) || defined(__EMSCRIPTEN__)
       int flags = ::fcntl(d, F_GETFL, 0);
       if (flags >= 0)
         ::fcntl(d, F_SETFL, flags & ~O_NONBLOCK);
-#else // defined(__SYMBIAN32__)
+#else // defined(__SYMBIAN32__) || defined(__EMSCRIPTEN__)
       ioctl_arg_type arg = 0;
       ::ioctl(d, FIONBIO, &arg);
-#endif // defined(__SYMBIAN32__)
+#endif // defined(__SYMBIAN32__) || defined(__EMSCRIPTEN__)
       state &= ~non_blocking;
 
       errno = 0;
@@ -87,7 +87,7 @@ bool set_user_non_blocking(int d, state_type& state,
   }
 
   errno = 0;
-#if defined(__SYMBIAN32__)
+#if defined(__SYMBIAN32__) || defined(__EMSCRIPTEN__)
   int result = error_wrapper(::fcntl(d, F_GETFL, 0), ec);
   if (result >= 0)
   {
@@ -95,10 +95,10 @@ bool set_user_non_blocking(int d, state_type& state,
     int flag = (value ? (result | O_NONBLOCK) : (result & ~O_NONBLOCK));
     result = error_wrapper(::fcntl(d, F_SETFL, flag), ec);
   }
-#else // defined(__SYMBIAN32__)
+#else // defined(__SYMBIAN32__) || defined(__EMSCRIPTEN__)
   ioctl_arg_type arg = (value ? 1 : 0);
   int result = error_wrapper(::ioctl(d, FIONBIO, &arg), ec);
-#endif // defined(__SYMBIAN32__)
+#endif // defined(__SYMBIAN32__) || defined(__EMSCRIPTEN__)
 
   if (result >= 0)
   {
@@ -137,7 +137,7 @@ bool set_internal_non_blocking(int d, state_type& state,
   }
 
   errno = 0;
-#if defined(__SYMBIAN32__)
+#if defined(__SYMBIAN32__) || defined(__EMSCRIPTEN__)
   int result = error_wrapper(::fcntl(d, F_GETFL, 0), ec);
   if (result >= 0)
   {
@@ -145,10 +145,10 @@ bool set_internal_non_blocking(int d, state_type& state,
     int flag = (value ? (result | O_NONBLOCK) : (result & ~O_NONBLOCK));
     result = error_wrapper(::fcntl(d, F_SETFL, flag), ec);
   }
-#else // defined(__SYMBIAN32__)
+#else // defined(__SYMBIAN32__) || defined(__EMSCRIPTEN__)
   ioctl_arg_type arg = (value ? 1 : 0);
   int result = error_wrapper(::ioctl(d, FIONBIO, &arg), ec);
-#endif // defined(__SYMBIAN32__)
+#endif // defined(__SYMBIAN32__) || defined(__EMSCRIPTEN__)
 
   if (result >= 0)
   {
diff --git a/asio/include/asio/detail/impl/socket_ops.ipp b/asio/include/asio/detail/impl/socket_ops.ipp
index 4b492daead..bacd6008ae 100644
--- a/asio/include/asio/detail/impl/socket_ops.ipp
+++ b/asio/include/asio/detail/impl/socket_ops.ipp
@@ -330,14 +330,14 @@ int close(socket_type s, state_type& state,
       ioctl_arg_type arg = 0;
       ::ioctlsocket(s, FIONBIO, &arg);
 #else // defined(ASIO_WINDOWS) || defined(__CYGWIN__)
-# if defined(__SYMBIAN32__)
+# if defined(__SYMBIAN32__) || defined(__EMSCRIPTEN__)
       int flags = ::fcntl(s, F_GETFL, 0);
       if (flags >= 0)
         ::fcntl(s, F_SETFL, flags & ~O_NONBLOCK);
-# else // defined(__SYMBIAN32__)
+# else // defined(__SYMBIAN32__) || defined(__EMSCRIPTEN__)
       ioctl_arg_type arg = 0;
       ::ioctl(s, FIONBIO, &arg);
-# endif // defined(__SYMBIAN32__)
+# endif // defined(__SYMBIAN32__) || defined(__EMSCRIPTEN__)
 #endif // defined(ASIO_WINDOWS) || defined(__CYGWIN__)
       state &= ~non_blocking;
 
@@ -368,7 +368,7 @@ bool set_user_non_blocking(socket_type s,
 #if defined(ASIO_WINDOWS) || defined(__CYGWIN__)
   ioctl_arg_type arg = (value ? 1 : 0);
   int result = error_wrapper(::ioctlsocket(s, FIONBIO, &arg), ec);
-#elif defined(__SYMBIAN32__)
+#elif defined(__SYMBIAN32__) || defined(__EMSCRIPTEN__)
   int result = error_wrapper(::fcntl(s, F_GETFL, 0), ec);
   if (result >= 0)
   {
@@ -421,7 +421,7 @@ bool set_internal_non_blocking(socket_type s,
 #if defined(ASIO_WINDOWS) || defined(__CYGWIN__)
   ioctl_arg_type arg = (value ? 1 : 0);
   int result = error_wrapper(::ioctlsocket(s, FIONBIO, &arg), ec);
-#elif defined(__SYMBIAN32__)
+#elif defined(__SYMBIAN32__) || defined(__EMSCRIPTEN__)
   int result = error_wrapper(::fcntl(s, F_GETFL, 0), ec);
   if (result >= 0)
   {
@@ -1762,6 +1762,9 @@ int select(int nfds, fd_set* readfds, fd_set* writefds,
     fd_set* exceptfds, timeval* timeout, asio::error_code& ec)
 {
   clear_last_error();
+#if defined(__EMSCRIPTEN__)
+  exceptfds = 0;
+#endif // defined(__EMSCRIPTEN__)
 #if defined(ASIO_WINDOWS) || defined(__CYGWIN__)
   if (!readfds && !writefds && !exceptfds && timeout)
   {