diff --git a/tests/errors/test_optional.py b/tests/errors/test_optional.py
new file mode 100644
index 0000000000..58786a1360
--- /dev/null
+++ b/tests/errors/test_optional.py
@@ -0,0 +1,2 @@
+def match(pat : str, string : str) -> Optional[list[str] | str]:
+    return None
\ No newline at end of file
diff --git a/tests/reference/asr-test_optional-97e5371.json b/tests/reference/asr-test_optional-97e5371.json
new file mode 100644
index 0000000000..7dbe53ca63
--- /dev/null
+++ b/tests/reference/asr-test_optional-97e5371.json
@@ -0,0 +1,13 @@
+{
+    "basename": "asr-test_optional-97e5371",
+    "cmd": "lpython --show-asr --no-color {infile} -o {outfile}",
+    "infile": "tests/errors/test_optional.py",
+    "infile_hash": "2532c73de47afb82c9d1d9fa335d3b274e7c79a14007353639958a45",
+    "outfile": null,
+    "outfile_hash": null,
+    "stdout": null,
+    "stdout_hash": null,
+    "stderr": "asr-test_optional-97e5371.stderr",
+    "stderr_hash": "b9cc75eb200847db5d4d39d9f511959ebf22faad68cf0096c7a2b68c",
+    "returncode": 2
+}
\ No newline at end of file
diff --git a/tests/reference/asr-test_optional-97e5371.stderr b/tests/reference/asr-test_optional-97e5371.stderr
new file mode 100644
index 0000000000..4c93a66d6b
--- /dev/null
+++ b/tests/reference/asr-test_optional-97e5371.stderr
@@ -0,0 +1,5 @@
+semantic error: The type 'Optional' is undeclared.
+ --> tests/errors/test_optional.py:1:39
+  |
+1 | def match(pat : str, string : str) -> Optional[list[str] | str]:
+  |                                       ^^^^^^^^^^^^^^^^^^^^^^^^^ 
diff --git a/tests/tests.toml b/tests/tests.toml
index 0c22c94aec..be2061fe97 100644
--- a/tests/tests.toml
+++ b/tests/tests.toml
@@ -1383,3 +1383,7 @@ run_with_dbg = true
 [[test]]
 filename = "runtime_errors/test_raise_01.py"
 run_with_dbg = true
+
+[[test]]
+filename = "errors/test_optional.py"
+asr = true
\ No newline at end of file