2 files changed, 12 insertions, 6 deletions
diff --git a/main.c b/main.c
index b2d169c..0cdb8a8 100644
--- a/main.c
+++ b/main.c
@@ -1429,13 +1429,18 @@ main (int argc, char **argv, char **envp)
 #ifdef HAVE_ISATTY
     if (isatty (fileno (stdout)))
       if (! lookup_variable (STRING_SIZE_TUPLE ("MAKE_TERMOUT")))
-        define_variable_cname ("MAKE_TERMOUT", TTYNAME (fileno (stdout)),
-                               o_default, 0)->export = v_export;
-
+        {
+          const char *tty = TTYNAME (fileno (stdout));
+          define_variable_cname ("MAKE_TERMOUT", tty ? tty : DEFAULT_TTYNAME,
+                                 o_default, 0)->export = v_export;
+        }
     if (isatty (fileno (stderr)))
       if (! lookup_variable (STRING_SIZE_TUPLE ("MAKE_TERMERR")))
-        define_variable_cname ("MAKE_TERMERR", TTYNAME (fileno (stderr)),
-                               o_default, 0)->export = v_export;
+        {
+          const char *tty = TTYNAME (fileno (stderr));
+          define_variable_cname ("MAKE_TERMERR", tty ? tty : DEFAULT_TTYNAME,
+                                 o_default, 0)->export = v_export;
+        }
 #endif
 
   /* Reset in case the switches changed our minds.  */
diff --git a/makeint.h b/makeint.h
index 6223936..2009f41 100644
--- a/makeint.h
+++ b/makeint.h
@@ -436,10 +436,11 @@ extern struct rlimit stack_limit;
 /* The number of bytes needed to represent the largest integer as a string.  */
 #define INTSTR_LENGTH         CSTRLEN ("18446744073709551616")
 
+#define DEFAULT_TTYNAME "true"
 #ifdef HAVE_TTYNAME
 # define TTYNAME(_f) ttyname (_f)
 #else
-# define TTYNAME(_f) "true"
+# define TTYNAME(_f) DEFAULT_TTYNAME
 #endif