diff --git a/src/fd.cpp b/src/fd.cpp
index 74db2241..a19da62f 100644
--- a/src/fd.cpp
+++ b/src/fd.cpp
@@ -1,9 +1,11 @@
 #ifdef _WIN32
 #ifndef FD_SETSIZE
-#define FD_SETSIZE 2048  // Set max fds - only for select() fallback
+#define FD_SETSIZE 2048  // set max fds - only for select() fallback on R <= 4.1
 #endif
+#define LATER POLL_FUNC WSAPoll
 #include <winsock2.h>
 #else
+#define LATER_POLL_FUNC poll
 #include <poll.h>
 #endif
 #include <Rcpp.h>
@@ -16,12 +18,6 @@
 
 #define LATER_INTERVAL 1024
 
-#ifdef _WIN32
-#define POLL_FUNC WSAPoll
-#else
-#define POLL_FUNC poll
-#endif
-
 typedef struct ThreadArgs_s {
   std::shared_ptr<std::atomic<bool>> flag;
   std::unique_ptr<Rcpp::Function> callback;
@@ -46,6 +42,9 @@ static void later_callback(void *arg) {
 
 // CONSIDER: if necessary to add method for HANDLES on Windows. Would be different code to SOCKETs.
 // TODO: implement re-usable background thread.
+
+#ifdef POLLIN // all platforms except R <= 4.1 on Windows
+
 static int wait_thread(void *arg) {
 
   std::unique_ptr<std::shared_ptr<ThreadArgs>> argsptr(static_cast<std::shared_ptr<ThreadArgs>*>(arg));
@@ -57,54 +56,6 @@ static int wait_thread(void *arg) {
   int timeoutms = infinite || args->timeout < 0 ? 1000 : (int) (args->timeout * 1000);
   int repeats = infinite || args->timeout < 0 ? 0 : timeoutms / LATER_INTERVAL;
 
-#ifndef POLLIN // fall back to select() for R <= 4.1 and older Windows
-
-  fd_set readfds, writefds, exceptfds;
-  FD_ZERO(&readfds);
-  FD_ZERO(&writefds);
-  FD_ZERO(&exceptfds);
-  const int max_fd = *std::max_element(args->fds->begin(), args->fds->end());
-  struct timeval tv;
-
-  do {
-    for (int i = 0; i < args->rfds; i++) {
-      FD_SET((*args->fds)[i], &readfds);
-    }
-    for (int i = args->rfds; i < (args->rfds + args->wfds); i++) {
-      FD_SET((*args->fds)[i], &writefds);
-    }
-    for (int i = args->rfds + args->wfds; i < args->num_fds; i++) {
-      FD_SET((*args->fds)[i], &exceptfds);
-    }
-    tv.tv_sec = (repeats ? LATER_INTERVAL : timeoutms) / 1000;
-    tv.tv_usec = ((repeats ? LATER_INTERVAL : timeoutms) % 1000) * 1000;
-
-    result = select(max_fd + 1, &readfds, &writefds, &exceptfds, &tv);
-
-    if (args->flag->load()) return 1;
-    if (result) break;
-  } while (infinite || (repeats-- && (timeoutms -= LATER_INTERVAL)));
-
-  if (result > 0) {
-    for (int i = 0; i < args->rfds; i++) {
-      (*args->fds)[i] = FD_ISSET((*args->fds)[i], &readfds);
-    }
-    for (int i = args->rfds; i < (args->rfds + args->wfds); i++) {
-      (*args->fds)[i] = FD_ISSET((*args->fds)[i], &writefds);
-    }
-    for (int i = args->rfds + args->wfds; i < args->num_fds; i++) {
-      (*args->fds)[i] = FD_ISSET((*args->fds)[i], &exceptfds);
-    }
-  } else if (result == 0) {
-    std::memset(args->fds->data(), 0, args->num_fds * sizeof(int));
-  } else {
-    for (int i = 0; i < args->num_fds; i++) {
-      (*args->fds)[i] = R_NaInt;
-    }
-  }
-
-#else
-
   std::vector<struct pollfd> pollfds;
   pollfds.reserve(args->num_fds);
   struct pollfd pfd;
@@ -128,7 +79,7 @@ static int wait_thread(void *arg) {
   }
 
   do {
-    result = POLL_FUNC(pollfds.data(), args->num_fds, repeats ? LATER_INTERVAL : timeoutms);
+    result = LATER_POLL_FUNC(pollfds.data(), args->num_fds, repeats ? LATER_INTERVAL : timeoutms);
     if (args->flag->load()) return 1;
     if (result) break;
   } while (infinite || (repeats-- && (timeoutms -= LATER_INTERVAL)));
@@ -151,7 +102,68 @@ static int wait_thread(void *arg) {
     }
   }
 
-#endif // POLLIN
+  execLaterNative2(later_callback, static_cast<void *>(argsptr.release()), 0, args->loop);
+
+  return 0;
+
+}
+
+#else // no POLLIN: fall back to select() for R <= 4.1 on Windows
+
+static int wait_thread(void *arg) {
+
+  std::unique_ptr<std::shared_ptr<ThreadArgs>> argsptr(static_cast<std::shared_ptr<ThreadArgs>*>(arg));
+  std::shared_ptr<ThreadArgs> args = *argsptr;
+
+  int result;
+
+  const bool infinite = args->timeout == R_PosInf;
+  int timeoutms = infinite || args->timeout < 0 ? 1000 : (int) (args->timeout * 1000);
+  int repeats = infinite || args->timeout < 0 ? 0 : timeoutms / LATER_INTERVAL;
+
+  fd_set readfds, writefds, exceptfds;
+  FD_ZERO(&readfds);
+  FD_ZERO(&writefds);
+  FD_ZERO(&exceptfds);
+  const int max_fd = *std::max_element(args->fds->begin(), args->fds->end());
+  struct timeval tv;
+
+  do {
+    for (int i = 0; i < args->rfds; i++) {
+      FD_SET((*args->fds)[i], &readfds);
+    }
+    for (int i = args->rfds; i < (args->rfds + args->wfds); i++) {
+      FD_SET((*args->fds)[i], &writefds);
+    }
+    for (int i = args->rfds + args->wfds; i < args->num_fds; i++) {
+      FD_SET((*args->fds)[i], &exceptfds);
+    }
+    tv.tv_sec = (repeats ? LATER_INTERVAL : timeoutms) / 1000;
+    tv.tv_usec = ((repeats ? LATER_INTERVAL : timeoutms) % 1000) * 1000;
+
+    result = select(max_fd + 1, &readfds, &writefds, &exceptfds, &tv);
+
+    if (args->flag->load()) return 1;
+    if (result) break;
+  } while (infinite || (repeats-- && (timeoutms -= LATER_INTERVAL)));
+
+  if (result > 0) {
+    for (int i = 0; i < args->rfds; i++) {
+      (*args->fds)[i] = FD_ISSET((*args->fds)[i], &readfds);
+    }
+    for (int i = args->rfds; i < (args->rfds + args->wfds); i++) {
+      (*args->fds)[i] = FD_ISSET((*args->fds)[i], &writefds);
+    }
+    for (int i = args->rfds + args->wfds; i < args->num_fds; i++) {
+      (*args->fds)[i] = FD_ISSET((*args->fds)[i], &exceptfds);
+    }
+  } else if (result == 0) {
+    std::memset(args->fds->data(), 0, args->num_fds * sizeof(int));
+  } else {
+    for (int i = 0; i < args->num_fds; i++) {
+      (*args->fds)[i] = R_NaInt;
+    }
+  }
 
   execLaterNative2(later_callback, static_cast<void *>(argsptr.release()), 0, args->loop);
 
@@ -159,6 +171,8 @@ static int wait_thread(void *arg) {
 
 }
 
+#endif // POLLIN
+
 // [[Rcpp::export]]
 Rcpp::RObject execLater_fd(Rcpp::Function callback, Rcpp::IntegerVector readfds, Rcpp::IntegerVector writefds,
                            Rcpp::IntegerVector exceptfds, Rcpp::NumericVector timeoutSecs, Rcpp::IntegerVector loop_id) {