diff --git a/CHANGELOG.md b/CHANGELOG.md
index 531c84eb..d02a8e1d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -34,6 +34,7 @@
   to fail.
 * Background color when alpha < 1.0 being wrong
   (https://codeberg.org/dnkl/foot/issues/249).
+* `generate-alt-random.py` failing in containers.
 
 
 ### Security
diff --git a/scripts/generate-alt-random-writes.py b/scripts/generate-alt-random-writes.py
index 202c99c5..2e51082b 100755
--- a/scripts/generate-alt-random-writes.py
+++ b/scripts/generate-alt-random-writes.py
@@ -37,11 +37,17 @@ def main():
     opts = parser.parse_args()
     out = opts.out if opts.out is not None else sys.stdout
 
-    lines, cols, height, width = struct.unpack(
-        'HHHH',
-        fcntl.ioctl(sys.stdout.fileno(),
-                    termios.TIOCGWINSZ,
-                    struct.pack('HHHH', 0, 0, 0, 0)))
+    try:
+        lines, cols, height, width = struct.unpack(
+            'HHHH',
+            fcntl.ioctl(sys.stdout.fileno(),
+                        termios.TIOCGWINSZ,
+                        struct.pack('HHHH', 0, 0, 0, 0)))
+    except OSError:
+        lines = None
+        cols = None
+        height = None
+        width = None
 
     if opts.rows is not None:
         lines = opts.rows
@@ -50,6 +56,9 @@ def main():
         cols = opts.cols
         width = 8 * cols     # PGO help binary hardcodes cell width to 8px
 
+    if lines is None or cols is None or height is None or width is None:
+        raise Exception('could not get terminal width/height; use --rows and --cols')
+
     # Number of characters to write to screen
     count = 256 * 1024**1