Index: libcfa/src/bits/signal.hfa
===================================================================
--- libcfa/src/bits/signal.hfa	(revision 2909b515da780ffca5028f3b4173e37403df5629)
+++ libcfa/src/bits/signal.hfa	(revision e0c235ca8e62339b4cd07c92fdf5cb4522119b86)
@@ -37,4 +37,7 @@
 
 	act.sa_sigaction = (void (*)(int, siginfo_t *, void *))handler;
+	sigemptyset( &act.sa_mask );
+	sigaddset( &act.sa_mask, SIGALRM );		// disabled during signal handler
+	sigaddset( &act.sa_mask, SIGUSR1 );
 	act.sa_flags = flags;