diff --git a/readpassphrase.h b/readpassphrase.h
index d4f8be7..328cd2a 100644
--- a/readpassphrase.h
+++ b/readpassphrase.h
@@ -6,8 +6,8 @@
 char* readpassphrase(const char* prompt, char* buf, size_t bufsz, int read_pw_from_stdin) {
     int n;
     int is_tty = !read_pw_from_stdin;
-    int infd = -1;
-    int outfd = -1;
+    int infd;
+    int outfd;
 
     struct termios term;
 
@@ -16,13 +16,9 @@ char* readpassphrase(const char* prompt, char* buf, size_t bufsz, int read_pw_fr
         outfd = 1;
         is_tty = tcgetattr(outfd, &term) == 0;
     } else {
-        for (int i = 0; i < 3; i++) {
-            if (tcgetattr(i, &term) == 0) {
-                infd = i;
-                outfd = i;
-                break;
-            }
-        }
+        infd = outfd = open("/dev/tty", O_RDWR);
+        if (!(infd >= 0 && tcgetattr(outfd, &term) == 0))
+            return NULL;
     }
 
     if (infd < 0)