diff --git a/programs/lib/libc/libc.c b/programs/lib/libc/libc.c
index a49da25..a92d6dc 100644
--- a/programs/lib/libc/libc.c
+++ b/programs/lib/libc/libc.c
@@ -103,6 +103,7 @@ static inline long _zos_syscall4(long nr, long a1, long a2, long a3, long a4) {
 #define SYS_GETMILLISECONDS 14
 #define SYS_GETCHAR 18
 #define SYS_GETCHAR_NB 166
+#define SYS_TERMINAL_ATTACHED 177
 #define SYS_SPAWN   20
 #define SYS_WAITPID 23
 #define SYS_GETARGS 25
@@ -2470,7 +2471,9 @@ char *getcwd(char *buf, size_t size) {
 }
 
 int isatty(int fd) {
-    return fd >= 0 && fd <= 2;
+    if (fd < STDIN_FILENO || fd > STDERR_FILENO)
+        return 0;
+    return _zos_syscall0(SYS_TERMINAL_ATTACHED) != 0;
 }
 
 /* ========================================================================