diff --git a/test/systemtest/conftest.py b/test/systemtest/conftest.py
index 7c8142b..6111534 100644
--- a/test/systemtest/conftest.py
+++ b/test/systemtest/conftest.py
@@ -116,7 +116,7 @@
 def fpga_uart(pytestconfig):
     """Return the path to the UART attached to the FPGA."""
     path = Path(pytestconfig.getoption('fpga_uart')).resolve()
-    assert path.is_file()
+    assert path.exists() and not path.is_dir()
     return path
 
 @pytest.fixture(scope="session")