diff --git a/src/backend/modern.lisp b/src/backend/modern.lisp
index 4f975a8..a0b8bd1 100644
--- a/src/backend/modern.lisp
+++ b/src/backend/modern.lisp
@@ -172,9 +172,20 @@ as a fallback when a keyword is not in *named-colors*.")
                  (sb-unix:unix-ioctl (sb-sys:fd-stream-fd (backend-output-stream b))
                                      +tiocgwinsz+
                                      (sb-alien:alien-sap winsize))
-                 (values (sb-alien:deref winsize 1)  ;; cols
-                         (sb-alien:deref winsize 0))) ;; rows
-            (sb-alien:free-alien winsize))))
+                     (values (sb-alien:deref winsize 1)  ;; cols
+                          (sb-alien:deref winsize 0))) ;; rows
+             (sb-alien:free-alien winsize))))
+      ;; $COLUMNS / $LINES env vars — set by every POSIX shell.
+      ;; Catches cases where ioctl on stdout's fd disagrees with
+      ;; the real terminal size (e.g. stdout redirected or a
+      ;; file descriptor mismatch).
+      (ignore-errors
+        (let ((cols (parse-integer (sb-ext:posix-getenv "COLUMNS")
+                                   :junk-allowed t))
+              (rows (parse-integer (sb-ext:posix-getenv "LINES")
+                                   :junk-allowed t)))
+          (when (and cols rows (> cols 0) (> rows 0))
+            (values cols rows))))
       (values 80 24)))
 
 (defmethod backend-write ((b modern-backend) string)
diff --git a/src/backend/simple.lisp b/src/backend/simple.lisp
index 0ca931f..4722ce4 100644
--- a/src/backend/simple.lisp
+++ b/src/backend/simple.lisp
@@ -39,6 +39,13 @@
                  (values (sb-alien:deref winsize 1)
                          (sb-alien:deref winsize 0)))
              (sb-alien:free-alien winsize))))
+      (ignore-errors
+        (let ((cols (parse-integer (sb-ext:posix-getenv "COLUMNS")
+                                   :junk-allowed t))
+              (rows (parse-integer (sb-ext:posix-getenv "LINES")
+                                   :junk-allowed t)))
+          (when (and cols rows (> cols 0) (> rows 0))
+            (values cols rows))))
       (values 80 24)))
 
 (defmethod backend-write ((b simple-backend) string)