diff --git a/src/common/compat.h b/src/common/compat.h
index dafd1339a5..d9cb5669d6 100644
--- a/src/common/compat.h
+++ b/src/common/compat.h
@@ -191,5 +191,11 @@ void tor_mutex_acquire(tor_mutex_t *m);
 void tor_mutex_release(tor_mutex_t *m);
 void tor_mutex_free(tor_mutex_t *m);
 
+#ifdef MS_WINDOWS
+#define TOR_IS_MULTITHREADED 1
+#else
+#undef TOR_IS_MULTITHREADED
+#endif
+
 #endif
 
diff --git a/src/or/cpuworker.c b/src/or/cpuworker.c
index b1fef2660b..c9ac3ebee4 100644
--- a/src/or/cpuworker.c
+++ b/src/or/cpuworker.c
@@ -210,7 +210,7 @@ static int cpuworker_main(void *data) {
   crypto_pk_env_t *onion_key = NULL, *last_onion_key = NULL;
 
   fd = fdarray[1]; /* this side is ours */
-#ifndef MS_WINDOWS
+#ifndef TOR_IS_MULTITHREADED
   tor_close_socket(fdarray[0]); /* this is the side of the socketpair the parent uses */
   connection_free_all(); /* so the child doesn't hold the parent's fd's open */
 #endif
@@ -282,7 +282,9 @@ static int spawn_cpuworker(void) {
 
   spawn_func(cpuworker_main, (void*)fd);
   log_fn(LOG_DEBUG,"just spawned a worker.");
+#ifndef TOR_IS_MULTITHREADED
   tor_close_socket(fd[1]); /* we don't need the worker's side of the pipe */
+#endif
 
   conn = connection_new(CONN_TYPE_CPUWORKER);
 
diff --git a/src/or/dns.c b/src/or/dns.c
index 57871bf23f..afc777dd7e 100644
--- a/src/or/dns.c
+++ b/src/or/dns.c
@@ -654,7 +654,7 @@ static int dnsworker_main(void *data) {
   int result;
 
   fd = fdarray[1]; /* this side is ours */
-#ifndef MS_WINDOWS
+#ifndef TOR_IS_MULTITHREADED
   tor_close_socket(fdarray[0]); /* this is the side of the socketpair the parent uses */
   connection_free_all(); /* so the child doesn't hold the parent's fd's open */
 #endif
@@ -716,7 +716,9 @@ static int spawn_dnsworker(void) {
 
   spawn_func(dnsworker_main, (void*)fd);
   log_fn(LOG_DEBUG,"just spawned a worker.");
+#ifndef TOR_IS_MULTITHREADED
   tor_close_socket(fd[1]); /* we don't need the worker's side of the pipe */
+#endif
 
   conn = connection_new(CONN_TYPE_DNSWORKER);