diff --git a/src/nwp_consumer/cmd/main.py b/src/nwp_consumer/cmd/main.py
index bad76b7e..37e86848 100644
--- a/src/nwp_consumer/cmd/main.py
+++ b/src/nwp_consumer/cmd/main.py
@@ -172,12 +172,14 @@ def main() -> None:
     """Entry point for the nwp-consumer CLI."""
     # Parse command line arguments from docstring
     arguments = docopt(__doc__, version=__version__)
+    erred = False
 
     programStartTime = dt.datetime.now()
     try:
         run(arguments=arguments)
     except Exception as e:
-        log.error("nwp-consumer error", error=str(e), exc_info=True)
+        log.error("encountered error running nwp-consumer", error=str(e), exc_info=True)
+        erred = True
     finally:
         leftoverTempPaths = list(internal.TMP_DIR.glob("*"))
         for p in leftoverTempPaths:
@@ -191,6 +193,8 @@ def main() -> None:
             elapsed_time=str(elapsedTime),
             version=__version__
         )
+        if erred:
+            exit(1)
 
 
 if __name__ == "__main__":
diff --git a/src/nwp_consumer/internal/inputs/ecmwf/mars.py b/src/nwp_consumer/internal/inputs/ecmwf/mars.py
index 03ca4716..63297f1e 100644
--- a/src/nwp_consumer/internal/inputs/ecmwf/mars.py
+++ b/src/nwp_consumer/internal/inputs/ecmwf/mars.py
@@ -123,6 +123,12 @@ def listRawFilesForInitTime(self, *, it: dt.datetime) \
         if it.hour not in [0, 12]:
             return []
 
+        # MARS requests can only ask for data that is more than 24 hours old: see
+        # https://confluence.ecmwf.int/display/UDOC/MARS+access+restrictions
+        if it > dt.datetime.utcnow() - dt.timedelta(hours=24):
+            raise ValueError("ECMWF MARS requests can only ask for data that is more than 24 hours old")
+            return []
+
         with tempfile.NamedTemporaryFile(suffix=".txt", mode="r+") as tf:
 
             marsReq: str = f"""
diff --git a/src/nwp_consumer/internal/inputs/icon/client.py b/src/nwp_consumer/internal/inputs/icon/client.py
index aa3d3fce..174192ba 100644
--- a/src/nwp_consumer/internal/inputs/icon/client.py
+++ b/src/nwp_consumer/internal/inputs/icon/client.py
@@ -57,11 +57,7 @@ def listRawFilesForInitTime(self, *, it: dt.datetime) -> list[internal.FileInfoM
         # ICON data is only available for today's date. If data hasn't been uploaded for that init
         # time yet, then yesterday's data will still be present on the server.
         if it.date() != dt.datetime.now(dt.timezone.utc).date():
-            log.warn(
-                event="ICON data is only available on today's date",
-                attempteddate=it.strftime("%Y-%m-%d"),
-                currentdate=dt.datetime.now(dt.timezone.utc).strftime("%Y-%m-%d"),
-            )
+            raise ValueError("ICON data is only available on today's date")
             return []
 
         # The ICON model only runs on the hours [00, 06, 12, 18]