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: