diff --git a/src/racket/src/places.c b/src/racket/src/places.c
index 12a5e820fc..692183aaac 100644
--- a/src/racket/src/places.c
+++ b/src/racket/src/places.c
@@ -592,6 +592,17 @@ void scheme_places_block_child_signal() XFORM_SKIP_PROC
   MZ_SIGSET(SIGCHLD, got_sigchld);
 }
 
+void scheme_places_unblock_child_signal() XFORM_SKIP_PROC
+{
+  sigset_t set;
+
+  MZ_SIGSET(SIGCHLD, SIG_IGN);
+
+  sigemptyset(&set);
+  sigaddset(&set, SIGCHLD);
+  sigprocmask(SIG_UNBLOCK, &set, NULL);
+}
+
 void scheme_places_start_child_signal_handler()
 {
   mz_proc_thread *signal_thread;
diff --git a/src/racket/src/port.c b/src/racket/src/port.c
index 8ee1d7282f..12f0255788 100644
--- a/src/racket/src/port.c
+++ b/src/racket/src/port.c
@@ -8106,6 +8106,9 @@ static Scheme_Object *subprocess(int c, Scheme_Object *args[])
 
 #if !defined(MZ_PLACES_WAITPID)
     scheme_block_child_signals(0);
+#else
+    if (!pid)
+      scheme_places_unblock_child_signal();
 #endif
   }
 
diff --git a/src/racket/src/schpriv.h b/src/racket/src/schpriv.h
index 11c7999202..c43b7b275b 100644
--- a/src/racket/src/schpriv.h
+++ b/src/racket/src/schpriv.h
@@ -3631,6 +3631,7 @@ Scheme_Object *scheme_places_deep_copy(Scheme_Object *so);
 # ifdef UNIX_PROCESSES
 # define MZ_PLACES_WAITPID
 void scheme_places_block_child_signal();
+void scheme_places_unblock_child_signal();
 void scheme_places_start_child_signal_handler();
 int scheme_get_child_status(int pid, int is_group, int *status);
 int scheme_places_register_child(int pid, int is_group, void *signal_fd, int *status);