diff --git a/src/ttyname.c b/src/ttyname.c
index 631372e8d..db5fb7155 100644
--- a/src/ttyname.c
+++ b/src/ttyname.c
@@ -1,7 +1,7 @@
 /*
  * SPDX-License-Identifier: ISC
  *
- * Copyright (c) 2012-2020 Todd C. Miller <Todd.Miller@sudo.ws>
+ * Copyright (c) 2012-2022 Todd C. Miller <Todd.Miller@sudo.ws>
  *
  * Permission to use, copy, modify, and distribute this software for any
  * purpose with or without fee is hereby granted, provided that the above
@@ -174,6 +174,17 @@ get_process_ttyname(char *name, size_t namelen)
 		goto done;
 	    }
 	}
+    } else {
+	struct stat sb;
+	int i;
+
+	/* Missing /proc/pid/psinfo file. */
+	for (i = STDIN_FILENO; i <= STDERR_FILENO; i++) {
+	    if (isatty(i) && fstat(i, &sb) != -1) {
+		ret = sudo_ttyname_dev(sb.st_rdev, name, namelen);
+		goto done;
+	    }
+	}
     }
     errno = ENOENT;
 
@@ -196,6 +207,7 @@ get_process_ttyname(char *name, size_t namelen)
     char *cp, buf[1024];
     char *ret = NULL;
     int serrno = errno;
+    pid_t ppid = 0;
     ssize_t nread;
     int fd;
     debug_decl(get_process_ttyname, SUDO_DEBUG_UTIL);
@@ -232,7 +244,8 @@ get_process_ttyname(char *name, size_t namelen)
 		while (*++ep != '\0') {
 		    if (*ep == ' ') {
 			*ep = '\0';
-			if (++field == 7) {
+			field++;
+			if (field == 7) {
 			    int tty_nr = sudo_strtonum(cp, INT_MIN, INT_MAX,
 				&errstr);
 			    if (errstr) {
@@ -253,12 +266,27 @@ get_process_ttyname(char *name, size_t namelen)
 			    }
 			    break;
 			}
+			if (field == 3) {
+			    ppid = sudo_strtonum(cp, INT_MIN, INT_MAX, NULL);
+			}
 			cp = ep + 1;
 		    }
 		}
 	    }
 	}
     }
+    if (ppid == 0) {
+	struct stat sb;
+	int i;
+
+	/* No parent pid found, /proc/self/stat is missing or corrupt. */
+	for (i = STDIN_FILENO; i <= STDERR_FILENO; i++) {
+	    if (isatty(i) && fstat(i, &sb) != -1) {
+		ret = sudo_ttyname_dev(sb.st_rdev, name, namelen);
+		goto done;
+	    }
+	}
+    }
     errno = ENOENT;
 
 done: