diff --git a/CHANGELOG.md b/CHANGELOG.md
index 663f40c6..ef9f00ce 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,7 @@
 
 ### Changed
 - `bashunit doc <filter>` says `No assertion matches '<filter>'` instead of printing nothing, which was indistinguishable from a broken install. Mirrors the existing `--custom` wording; the exit code stays 0 because `doc` is informational (#1201)
+- `install.sh` destination errors no longer advise a `-d` flag that does not exist — the script takes positional arguments, so following the advice produced `Invalid arguments`. The one message whose job is to tell you how to recover pointed at a form the parser rejects (#1221)
 - The `example/` demo is covered by the suite. `docs/examples.md` and `example/README.md` send new users to `./bashunit example` as their first contact with the framework, and nothing ran it — `make test` collects from `tests/` only — so it could break while CI stayed green. The dead `EXAMPLE_TEST_SCRIPTS` variable, pointing at a file deleted several releases ago, is gone with it (#1219)
 - Docs: an empty entry in the `-e/--env/--boot` file assigns an empty value rather than restoring the built-in default, so blanking a boolean disables it; the guide said it "wipes" the value, which reads as a reset. The rest of the precedence ladder is now covered by tests (#1217)
 - Docs: the test-function name rule is stated correctly — the prefix is a literal, lowercase `test_`, so the guide's own `testRenderAllTestsPassedWhenNotFailedTests` example and its claim that names are case-insensitive were both wrong, and a function named either way is silently never run (#1215)
diff --git a/install.sh b/install.sh
index d72cf63b..7432666e 100755
--- a/install.sh
+++ b/install.sh
@@ -199,19 +199,19 @@ cd "$(dirname "$0")"
 # directory` with no mention of bashunit at all (#1197).
 if [ -e "$DIR" ] && [ ! -d "$DIR" ]; then
   echo "Error: '$DIR' exists and is not a directory." >&2
-  echo "Choose another destination with -d, or remove that file." >&2
+  echo "Choose another destination by passing it as an argument, or remove that file." >&2
   exit 1
 fi
 
 if [ ! -d "$DIR" ] && ! mkdir -p "$DIR" 2>/dev/null; then
   echo "Error: cannot create the '$DIR' folder." >&2
-  echo "Choose another destination with -d, or re-run with sufficient permissions." >&2
+  echo "Choose another destination by passing it as an argument, or re-run with sufficient permissions." >&2
   exit 1
 fi
 
 if [ ! -w "$DIR" ]; then
   echo "Error: cannot write to the '$DIR' folder." >&2
-  echo "Choose another destination with -d, or re-run with sufficient permissions." >&2
+  echo "Choose another destination by passing it as an argument, or re-run with sufficient permissions." >&2
   exit 1
 fi
 
diff --git a/tests/acceptance/install_test.sh b/tests/acceptance/install_test.sh
index dcb0a32b..5f261ff4 100644
--- a/tests/acceptance/install_test.sh
+++ b/tests/acceptance/install_test.sh
@@ -344,3 +344,48 @@ function test_install_rejects_a_destination_it_cannot_write() {
   assert_general_error "" "" "$ec"
   assert_contains "cannot write to" "$output"
 }
+
+# The three destination errors above all end with advice on how to recover, and
+# the advice named a `-d` flag the script never had -- `install.sh` parses
+# positional arguments only, so following it produced "Invalid arguments"
+# (#1221). The assertions covered the diagnosis line and stopped there, which is
+# exactly how an invented flag survives.
+#
+# So run the suggested form instead of string-matching it. This needs no network:
+# the destination is validated first, and an unparseable argument is rejected
+# before that.
+function test_the_recovery_advice_names_a_form_the_parser_accepts() {
+  local dir
+  dir="$(bashunit::temp_dir)"
+  cp ./install.sh "$dir/install.sh"
+  printf 'not a dir\n' >"$dir/blocked"
+
+  local output
+  output=$(cd "$dir" && ./install.sh 0.47.0 blocked 2>&1) || true
+  assert_contains "Choose another destination" "$output"
+
+  # The advice must not name a flag. Asserted against the run that actually
+  # prints it: a flag-shaped argument dies in the parser before any of this,
+  # so checking the advice there would compare against nothing at all.
+  assert_not_contains "-d" "$output"
+
+  # And what it does tell the reader to do -- pass a different destination as
+  # an argument -- has to get past argument parsing.
+  local retry
+  retry=$(cd "$dir" && ./install.sh 0.47.0 elsewhere 2>&1) || true
+
+  assert_not_contains "Invalid arguments" "$retry"
+}
+
+# The parser takes positional arguments only, which is what the advice above
+# now describes.
+function test_a_flag_shaped_destination_is_rejected() {
+  local dir
+  dir="$(bashunit::temp_dir)"
+  cp ./install.sh "$dir/install.sh"
+
+  local output
+  output=$(cd "$dir" && ./install.sh -d somewhere 2>&1) || true
+
+  assert_contains "Invalid arguments" "$output"
+}