diff --git a/src/pygama/flow/data_loader.py b/src/pygama/flow/data_loader.py
index aa65d2a3c..e2c9f6c5f 100644
--- a/src/pygama/flow/data_loader.py
+++ b/src/pygama/flow/data_loader.py
@@ -1411,7 +1411,7 @@ def load_iterator(
                             )
                             for file in gb.groups.keys()
                         ]
-                        tb_names += [self.filedb.get_table_name(tier, tb)] * len(gb)
+                        tb_names += [[self.filedb.get_table_name(tier, tb)]] * len(gb)
                         idx_list += [
                             list(entry_list.loc[i, f"{level}_idx"])
                             for i in gb.groups.values()
@@ -1509,7 +1509,7 @@ def browse(
                     )
                     for file in gb.groups.keys()
                 ]
-                tb_names += [self.filedb.get_table_name(tier, tb)] * len(gb)
+                tb_names += [[self.filedb.get_table_name(tier, tb)]] * len(gb)
                 idx_list += [
                     list(entry_list.loc[i, f"{parent}_idx"]) for i in gb.groups.values()
                 ]
diff --git a/src/pygama/utils.py b/src/pygama/utils.py
index 888ca396c..b6b73d26c 100644
--- a/src/pygama/utils.py
+++ b/src/pygama/utils.py
@@ -51,7 +51,7 @@ class NumbaPygamaDefaults(MutableMapping):
     """
 
     def __init__(self) -> None:
-        self.parallel: bool = getenv_bool("PYGAMA_PARALLEL", default=True)
+        self.parallel: bool = getenv_bool("PYGAMA_PARALLEL", default=False)
         self.fastmath: bool = getenv_bool("PYGAMA_FASTMATH", default=True)
 
     def __getitem__(self, item: str) -> Any:
diff --git a/tests/test_utils.py b/tests/test_utils.py
index ba70ad382..95e3f1b2c 100644
--- a/tests/test_utils.py
+++ b/tests/test_utils.py
@@ -3,7 +3,7 @@
 
 def test_math_numba_defaults():
     assert pgu.numba_math_defaults_kwargs.fastmath
-    assert pgu.numba_math_defaults_kwargs.parallel
+    assert not pgu.numba_math_defaults_kwargs.parallel
 
     pgu.numba_math_defaults.fastmath = False
-    assert ~pgu.numba_math_defaults.fastmath
+    assert not pgu.numba_math_defaults.fastmath