diff --git a/metaflow_extensions/slurm_ext/plugins/slurm/slurm_client.py b/metaflow_extensions/slurm_ext/plugins/slurm/slurm_client.py
index c75130d..0959180 100644
--- a/metaflow_extensions/slurm_ext/plugins/slurm/slurm_client.py
+++ b/metaflow_extensions/slurm_ext/plugins/slurm/slurm_client.py
@@ -38,6 +38,17 @@ def __init__(
                 % sys.executable
             )
 
+        for param, env_var in [
+            ("ssh_key_file", "METAFLOW_SLURM_SSH_KEY_FILE"),
+            ("username", "METAFLOW_SLURM_USERNAME"),
+            ("address", "METAFLOW_SLURM_ADDRESS"),
+        ]:
+            if locals()[param] is None:
+                raise SlurmException(
+                    "%s is required. Set it via @slurm(%s=...) "
+                    "or the %s environment variable." % (param, param, env_var)
+                )
+
         ssh_key_file_path = Path(ssh_key_file).expanduser().resolve()
         cert_file_path = Path(cert_file).expanduser().resolve() if cert_file else None