diff --git a/include/linux/x86/syscall.h b/include/linux/x86/syscall.h
index dd063c82..4414d3c1 100644
--- a/include/linux/x86/syscall.h
+++ b/include/linux/x86/syscall.h
@@ -79,4 +79,7 @@
 #define SYS_getegid   0x32
 #define SYS_setgid    0x3e
 
+// make+POSIX
+#define SYS_sigprocmask 0x7e
+
 #endif // __MES_LINUX_X86_SYSCALL_H
diff --git a/include/linux/x86_64/syscall.h b/include/linux/x86_64/syscall.h
index fddce5c4..0c73df78 100644
--- a/include/linux/x86_64/syscall.h
+++ b/include/linux/x86_64/syscall.h
@@ -75,4 +75,7 @@
 #define SYS_geteuid   0x6b
 #define SYS_getegid   0x6c
 
+// make+POSIX
+#define SYS_rt_sigprocmask 0x0e
+
 #endif // __MES_LINUX_X86_64_SYSCALL_H
diff --git a/include/signal.h b/include/signal.h
index 21079bac..bfb18b1c 100644
--- a/include/signal.h
+++ b/include/signal.h
@@ -228,6 +228,12 @@ void* signal (int signum, void * action);
 sighandler_t signal (int signum, sighandler_t action);
 #endif
 int sigemptyset (sigset_t *set);
+#ifndef SIG_BLOCK
+#define SIG_BLOCK 0
+#define SIG_UNBLOCK 1
+#define SIG_SETMASK 2
+#endif
+int sigprocmask (int how, sigset_t const *set, sigset_t *oldset);
 
 #endif //! WITH_GLIBC
 
diff --git a/include/unistd.h b/include/unistd.h
index d6c218e4..8810cbf4 100644
--- a/include/unistd.h
+++ b/include/unistd.h
@@ -29,7 +29,9 @@
 
 #else // ! WITH_GLIBC
 
+#if defined (BOOTSTRAP_WITH_POSIX)
 #define _POSIX_VERSION 199009L
+#endif
 
 #include <sys/types.h>
 #ifndef NULL
diff --git a/lib/linux/gnu.c b/lib/linux/gnu.c
index bd914d28..753713ff 100644
--- a/lib/linux/gnu.c
+++ b/lib/linux/gnu.c
@@ -198,3 +198,14 @@ setgid (gid_t newgid)
 {
   return _sys_call1 (SYS_setgid, (long)newgid);
 }
+
+// make+POSIX
+int
+sigprocmask (int how, sigset_t const *set, sigset_t *oldset)
+{
+#if __i386__
+  return _sys_call3 (SYS_sigprocmask, (long)how, (long)set, (long)oldset);
+#else
+  return _sys_call3 (SYS_rt_sigprocmask, (long)how, (long)set, (long)oldset);
+#endif
+}