diff --git a/build-aux/configure-lib.sh b/build-aux/configure-lib.sh
index edae972e..8be65233 100644
--- a/build-aux/configure-lib.sh
+++ b/build-aux/configure-lib.sh
@@ -396,6 +396,7 @@ lib/stub/setvbuf.c
 lib/stub/sigaddset.c
 lib/stub/sigblock.c
 lib/stub/sigdelset.c
+lib/stub/sigfillset.c
 lib/stub/sigsetmask.c
 lib/stub/sin.c
 lib/stub/sqrt.c
diff --git a/include/signal.h b/include/signal.h
index 84924770..48dfbc94 100644
--- a/include/signal.h
+++ b/include/signal.h
@@ -251,6 +251,7 @@ int sigaction (int signum, struct sigaction const *act, struct sigaction *oldact
 int sigaddset (sigset_t *set, int signum);
 int sigdelset (sigset_t *set, int signum);
 int sigemptyset (sigset_t *set);
+int sigfillset (sigset_t *set);
 #if __MESC__
 void *signal (int signum, void *action);
 #else
diff --git a/lib/stub/sigfillset.c b/lib/stub/sigfillset.c
new file mode 100644
index 00000000..515e4c8d
--- /dev/null
+++ b/lib/stub/sigfillset.c
@@ -0,0 +1,33 @@
+/* -*-comment-start: "//";comment-end:""-*-
+ * GNU Mes --- Maxwell Equations of Software
+ * Copyright © 2022 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
+ *
+ * This file is part of GNU Mes.
+ *
+ * GNU Mes is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or (at
+ * your option) any later version.
+ *
+ * GNU Mes is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with GNU Mes.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <mes/lib.h>
+#include <signal.h>
+
+int
+sigfillset (sigset_t *set)
+{
+  static int stub = 0;
+  if (__mes_debug () && !stub)
+    eputs ("sigfillset stub\n");
+  stub = 1;
+  errno = 0;
+  return 0;
+}