Index: src/libcfa/concurrency/preemption.c
===================================================================
--- src/libcfa/concurrency/preemption.c	(revision de94a60491c1429f478b0393f4b57a8200aee916)
+++ src/libcfa/concurrency/preemption.c	(revision ade52728204b1fb638e539ca3bc2ea5abb2d80a2)
@@ -357,10 +357,11 @@
 	// Block sigalrms to control when they arrive
 	sigset_t mask;
+	sigfillset(&mask);
+	if ( pthread_sigmask( SIG_BLOCK, &mask, NULL ) == -1 ) {
+	    abort( "internal error, pthread_sigmask" );
+	}
+
 	sigemptyset( &mask );
 	sigaddset( &mask, SIGALRM );
-
-	if ( pthread_sigmask( SIG_BLOCK, &mask, NULL ) == -1 ) {
-	    abort( "internal error, pthread_sigmask" );
-	}
 
 	// Main loop