diff --git a/chronos/osdefs.nim b/chronos/osdefs.nim
index 8365297..d7bb868 100644
--- a/chronos/osdefs.nim
+++ b/chronos/osdefs.nim
@@ -825,7 +825,7 @@ elif defined(macos) or defined(macosx):
   from std/posix import close, shutdown, socket, getpeername, getsockname,
                         recvfrom, sendto, send, bindSocket, recv, connect,
                         unlink, listen, getaddrinfo, gai_strerror, getrlimit,
-                        setrlimit, getpid, pthread_sigmask, sigemptyset,
+                        setrlimit, getpid, pthread_sigmask, sigprocmask, sigemptyset,
                         sigaddset, sigismember, fcntl, accept, pipe, write,
                         signal, read, setsockopt, getsockopt,
                         Timeval, Timespec, Pid, Mode, Time, Sigset, SockAddr,
@@ -844,7 +844,7 @@ elif defined(macos) or defined(macosx):
   export close, shutdown, socket, getpeername, getsockname,
          recvfrom, sendto, send, bindSocket, recv, connect,
          unlink, listen, getaddrinfo, gai_strerror, getrlimit,
-         setrlimit, getpid, pthread_sigmask, sigemptyset,
+         setrlimit, getpid, pthread_sigmask, sigprocmask, sigemptyset,
          sigaddset, sigismember, fcntl, accept, pipe, write,
          signal, read, setsockopt, getsockopt,
          Timeval, Timespec, Pid, Mode, Time, Sigset, SockAddr,