diff --git a/m4/sched_h.m4 b/m4/sched_h.m4
index 931358f..d62bc9b 100644
--- a/m4/sched_h.m4
+++ b/m4/sched_h.m4
@@ -10,6 +10,7 @@ AC_DEFUN([gl_SCHED_H],
 [
   AC_COMPILE_IFELSE(
     [AC_LANG_PROGRAM([[
+       #include <errno.h>
        #include <sched.h>
        struct sched_param a;
        int b[] = { SCHED_FIFO, SCHED_RR, SCHED_OTHER };
@@ -29,7 +30,8 @@ AC_DEFUN([gl_SCHED_H],

      AC_CHECK_TYPE([struct sched_param],
        [HAVE_STRUCT_SCHED_PARAM=1], [HAVE_STRUCT_SCHED_PARAM=0],
-       [#include <sched.h>])
+       [#include <errno.h>
+        #include <sched.h>])
      AC_SUBST([HAVE_STRUCT_SCHED_PARAM])

      dnl Ensure the type pid_t gets defined.
diff --git a/tests/test-sched.c b/tests/test-sched.c
index 5a64120..c118b5e 100644
--- a/tests/test-sched.c
+++ b/tests/test-sched.c
@@ -18,6 +18,7 @@

 #include <config.h>

+#include <errno.h>
 #include <sched.h>

 /* Check that 'struct sched_param' is defined.  */