diff --git a/src/xz/args.c b/src/xz/args.c
index be26bf3d..7468a496 100644
--- a/src/xz/args.c
+++ b/src/xz/args.c
@@ -25,7 +25,7 @@ bool opt_robot = false;
 
 // We don't modify or free() this, but we need to assign it in some
 // non-const pointers.
-const char *stdin_filename = "(stdin)";
+const char *const stdin_filename = "(stdin)";
 
 
 static void
diff --git a/src/xz/args.h b/src/xz/args.h
index ac5959b5..d01033c8 100644
--- a/src/xz/args.h
+++ b/src/xz/args.h
@@ -37,6 +37,6 @@ extern bool opt_keep_original;
 // extern bool opt_recursive;
 extern bool opt_robot;
 
-extern const char *stdin_filename;
+extern const char *const stdin_filename;
 
 extern void args_parse(args_info *args, int argc, char **argv);