diff --git a/model_ensembler/__init__.py b/model_ensembler/__init__.py
index 6f564b5..0786f2a 100644
--- a/model_ensembler/__init__.py
+++ b/model_ensembler/__init__.py
@@ -2,4 +2,4 @@
 
 __author__ = """James Byrne"""
 __email__ = 'jambyr@bas.ac.uk'
-__version__ = '0.5.5'
+__version__ = '0.5.6a0'
diff --git a/model_ensembler/batcher.py b/model_ensembler/batcher.py
index e022c4a..19f097b 100644
--- a/model_ensembler/batcher.py
+++ b/model_ensembler/batcher.py
@@ -155,9 +155,13 @@ def do_batch_execution(loop, batch, repeat=False):
     skip_indexes = args.indexes if args.indexes else list()
     batch_ctx.set(batch)
 
-    batch_dict = {k: v for k, v in batch._asdict().items() \
-                  if not (k.startswith("pre_") or k.startswith("post_")
-                          or k == "runs")}
+    batch_dict = {k: v
+                  for k, v in batch._asdict().items() \
+                  if not (k.startswith("pre_")
+                          or k.startswith("post_")
+                          or k in "runs")
+                  and not (k in ["cluster", "email", "nodes", "ntasks", "length"]
+                           and v is None)}
 
     run_vars = run_ctx.get()
     run_vars.update(batch_dict)
diff --git a/model_ensembler/config.py b/model_ensembler/config.py
index 9a70a12..b81f97e 100644
--- a/model_ensembler/config.py
+++ b/model_ensembler/config.py
@@ -165,7 +165,7 @@ def vars(self):
 BatchSpec.__new__.__defaults__ = (None, [], None,
                                   None, None,
                                   [], 0, 0, False,
-                                  None, None, None, 0,
+                                  None, None, None, None,
                                   None,
                                   [], [], [], [])
 
diff --git a/pyproject.toml b/pyproject.toml
deleted file mode 100644
index 1ca1d09..0000000
--- a/pyproject.toml
+++ /dev/null
@@ -1,2 +0,0 @@
-[project]
-name = "model-ensembler"