diff --git a/m4/ssize_t.m4 b/m4/ssize_t.m4
new file mode 100644
index 000000000..c97ab2ec0
--- /dev/null
+++ b/m4/ssize_t.m4
@@ -0,0 +1,22 @@
+#serial 1
+
+AC_PREREQ(2.14a)
+
+dnl This is a specialization of AC_CHECK_TYPE applied to `ssize_t' with
+dnl the difference that it also includes unistd.h on systems that have it.
+dnl On Fujitsu UXP/V systems ssize_t is defined in unistd.h.
+AC_DEFUN(AC_TYPE_SSIZE_T,
+  [
+    AC_CHECK_HEADERS(unistd.h)
+    AC_CHECK_TYPE(ssize_t, int,
+      [
+#include <sys/types.h>
+#if STDC_HEADERS
+# include <stdlib.h>
+# include <stddef.h>
+#endif
+#if HAVE_UNISTD_H
+# include <unistd.h>
+#endif
+      ]
+  )])