diff --git a/include/limits.h b/include/limits.h
index 5a19b10f..4e79c5b0 100644
--- a/include/limits.h
+++ b/include/limits.h
@@ -33,6 +33,7 @@
 #define UCHAR_MAX 255
 #define CHAR_MAX 255
 #define UINT_MAX 4294967295U
+#define ULONG_MAX 4294967295U
 #define INT_MIN -2147483648
 #define INT_MAX 2147483647
 #define MB_CUR_MAX 1
diff --git a/include/locale.h b/include/locale.h
index 18eb2914..fd9bbdc6 100644
--- a/include/locale.h
+++ b/include/locale.h
@@ -1,6 +1,6 @@
 /* -*-comment-start: "//";comment-end:""-*-
  * GNU Mes --- Maxwell Equations of Software
- * Copyright © 2017 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
+ * Copyright © 2017,2018 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
  *
  * This file is part of GNU Mes.
  *
@@ -28,7 +28,13 @@
 #include_next <locale.h>
 
 #else // ! WITH_GLIBC
-char* dirname (char*);
+
+#ifndef LC_ALL
+#define LC_ALL     "LC_ALL"
+#define LC_NUMERIC "LC_NUMERIC"
+#endif
+char * setlocale (int category, char const *locale);
+
 #endif // ! WITH_GLIBC
 
 #endif // __MES_LOCALE_H
diff --git a/include/signal.h b/include/signal.h
index 3d7f69c5..bd7e0404 100644
--- a/include/signal.h
+++ b/include/signal.h
@@ -210,6 +210,7 @@ typedef struct ucontext
 
 int kill (pid_t pid, int signum);
 int sigaction (int signum, struct sigaction const *act, struct sigaction *oldact);
+int sigaddset (sigset_t *set, int signum);
 #if __MESC__
 void* signal (int signum, void * action);
 #else
diff --git a/lib/libc+gnu.c b/lib/libc+gnu.c
index 9fb90018..4f997e2f 100644
--- a/lib/libc+gnu.c
+++ b/lib/libc+gnu.c
@@ -111,3 +111,5 @@
 #include <stub/getlogin.c>
 #include <stub/setvbuf.c>
 #include <stub/sigblock.c>
+#include <stub/sigaddset.c>
+#include <stub/setlocale.c>
diff --git a/lib/stub/setlocale.c b/lib/stub/setlocale.c
new file mode 100644
index 00000000..e4fe783f
--- /dev/null
+++ b/lib/stub/setlocale.c
@@ -0,0 +1,28 @@
+/* -*-comment-start: "//";comment-end:""-*-
+ * GNU Mes --- Maxwell Equations of Software
+ * Copyright © 2018 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 <libmes.h>
+#include <locale.h>
+
+char *
+setlocale (int category, char const *locale)
+{
+  return "C";
+}
diff --git a/lib/stub/sigaddset.c b/lib/stub/sigaddset.c
new file mode 100644
index 00000000..063c5ac9
--- /dev/null
+++ b/lib/stub/sigaddset.c
@@ -0,0 +1,28 @@
+/* -*-comment-start: "//";comment-end:""-*-
+ * GNU Mes --- Maxwell Equations of Software
+ * Copyright © 2018 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 <libmes.h>
+#include <signal.h>
+
+int
+sigaddset (sigset_t *set, int signum)
+{
+  return 0;
+}