--- src/lib/libpthread/thread/thr_sigmask.c	Tue Apr 12 23:52:34 2005
+++ src/lib/libpthread/thread/thr_sigmask.c	Mon May  9 18:40:02 2005
@@ -49,7 +49,7 @@
 	sigset_t oldset, newset;
 	int ret;
 
-	if (curthread->attr.flags & PTHREAD_SCOPE_SYSTEM) {
+	if (curthread->attr.flags & PTHREAD_SCOPE_SYSTEM && _kse_isthreaded()) {
 		ret = __sys_sigprocmask(how, set, oset);
 		if (ret != 0)
 			ret = errno;