Index: libgfortran/io/unix.c
===================================================================
--- libgfortran/io/unix.c	(revision 170899)
+++ libgfortran/io/unix.c	(working copy)
@@ -1055,7 +1055,8 @@ tempfile (st_parameter_open *opp)
      )
     slash = "";
 
-  template = get_mem (strlen (tempdir) + 20);
+  // The maximal string length is in the mktemp() case below.
+  template = get_mem (strlen (tempdir) + 23);
 
 #ifdef HAVE_MKSTEMP
   sprintf (template, "%s%sgfortrantmpXXXXXX", tempdir, slash);
@@ -1066,7 +1067,17 @@ tempfile (st_parameter_open *opp)
   fd = -1;
   do
     {
-      sprintf (template, "%s%sgfortrantmpXXXXXX", tempdir, slash);
+      /* Some implementations of mktemp(), following old BSD behavior,
+	 only allow 26 different names. So, we add a short almost-unique
+	 prefix ourselves, to work around this issue.  */
+      static int count = 0;
+      char l3 = 'a' + count % 26;
+      char l2 = 'a' + (count / 26) % 26;
+      char l1 = 'a' + (count / (26 * 26)) % 26;
+      count++;
+      sprintf (template, "%s%sgfortrantmp%c%c%cXXXXXX", tempdir, slash,
+	       l1, l2, l3);
+
       if (!mktemp (template))
 	break;
 #if defined(HAVE_CRLF) && defined(O_BINARY)