diff --git a/src/aarecommon/config/beamline.py b/src/aarecommon/config/beamline.py
index 9f18142..8ca01e8 100644
--- a/src/aarecommon/config/beamline.py
+++ b/src/aarecommon/config/beamline.py
@@ -29,9 +29,13 @@ class BeamlineYAMLConfig:
 def mx_beamline() -> MXBeamline:
     name = os.getenv("BEAMLINE")
     if name is None:
-        return MXBeamline.SIMULATED
+        raise ValueError("Please set the BEAMLINE environment variable to run AareDAQ")
     name = name.strip().upper()
-    return MXBeamline[name] if name in MXBeamline.__members__ else MXBeamline.SIMULATED
+    if name in MXBeamline.__members__:
+        return MXBeamline[name]
+    raise ValueError(
+        f"{name} is not a valid value for BEAMLINE. Please set one of {MXBeamline.__members__}"
+    )
 
 
 def get_jfjoch_url(bl: MXBeamline) -> str:
diff --git a/tests/test_beamline.py b/tests/test_beamline.py
index acc8ea5..dadcb9c 100644
--- a/tests/test_beamline.py
+++ b/tests/test_beamline.py
@@ -1,14 +1,18 @@
 import os
 from unittest.mock import patch
 
-from aarecommon.models.beamline import MXBeamline
+import pytest
+
 from aarecommon.config.beamline import mx_beamline
+from aarecommon.models.beamline import MXBeamline
 
 
 def test_mx_beamline_default():
     with patch.dict(os.environ, {}, clear=True):
-        # If BEAMLINE is not set, it should return SIMULATED
-        assert mx_beamline() == MXBeamline.SIMULATED
+        with pytest.raises(ValueError) as e:
+            # If BEAMLINE is not set, it should raise
+            mx_beamline()
+    assert e.match("set the BEAMLINE")
 
 
 def test_mx_beamline_x10sa():
@@ -22,5 +26,7 @@ def test_mx_beamline_x06sa():
 
 
 def test_mx_beamline_invalid():
-    with patch.dict(os.environ, {"BEAMLINE": "INVALID"}):
-        assert mx_beamline() == MXBeamline.SIMULATED
+    with pytest.raises(ValueError) as e:
+        with patch.dict(os.environ, {"BEAMLINE": "INVALID"}):
+            mx_beamline()
+        assert e.match("not a valid value")