diff --git a/programs/fileio.h b/programs/fileio.h
index 60a7e0de8..a740f35ef 100644
--- a/programs/fileio.h
+++ b/programs/fileio.h
@@ -18,8 +18,8 @@ extern "C" {
 /* *************************************
 *  Special i/o constants
 **************************************/
-#define stdinmark "stdin"
-#define stdoutmark "stdout"
+#define stdinmark "/*stdin*\\"
+#define stdoutmark "/*stdout*\\"
 #ifdef _WIN32
 #  define nulmark "nul"
 #else