diff --git a/validphys2/src/validphys/filters.py b/validphys2/src/validphys/filters.py
index 91c80ce2fb..ad3e300070 100644
--- a/validphys2/src/validphys/filters.py
+++ b/validphys2/src/validphys/filters.py
@@ -110,7 +110,7 @@ def filter_closure_data(filter_path, data, fakepdf, fakenoise, filterseed, sep_m
 
 
 def filter_closure_data_by_experiment(
-    filter_path, experiments_data, fakepdf, fakenoise, filterseed, experiments_index, sep_mult
+    filter_path, experiments_data, fakepdf, fakenoise, filterseed, data_index, sep_mult
 ):
     """
     Like :py:func:`filter_closure_data` except filters data by experiment.
@@ -124,7 +124,7 @@ def filter_closure_data_by_experiment(
 
     res = []
     for exp in experiments_data:
-        experiment_index = experiments_index[experiments_index.isin([exp.name], level=0)]
+        experiment_index = data_index[data_index.isin([exp.name], level=0)]
         res.append(
             _filter_closure_data(
                 filter_path, exp, fakepdf, fakenoise, filterseed, experiment_index, sep_mult
@@ -179,7 +179,7 @@ def _filter_real_data(filter_path, data):
 
 
 def _filter_closure_data(
-    filter_path, data, fakepdf, fakenoise, filterseed, experiments_index, sep_mult
+    filter_path, data, fakepdf, fakenoise, filterseed, data_index, sep_mult
 ):
     """
     This function is accessed within a closure test only, that is, the fakedata
@@ -213,7 +213,7 @@ def _filter_closure_data(
                  random noise added to Level 0 data
 
 
-    experiments_index : pandas.MultiIndex
+    data_index : pandas.MultiIndex
 
 
     Returns
@@ -241,7 +241,7 @@ def _filter_closure_data(
     if fakenoise:
         # ======= Level 1 closure test =======#
 
-        closure_data = make_level1_data(data, closure_data, filterseed, experiments_index, sep_mult)
+        closure_data = make_level1_data(data, closure_data, filterseed, data_index, sep_mult)
 
     # ====== write commondata and systype files ======#
     if fakenoise:
diff --git a/validphys2/src/validphys/pseudodata.py b/validphys2/src/validphys/pseudodata.py
index 84019e18b3..91d92dda1c 100644
--- a/validphys2/src/validphys/pseudodata.py
+++ b/validphys2/src/validphys/pseudodata.py
@@ -293,7 +293,7 @@ def level0_commondata_wc(data, fakepdf):
     return level0_commondata_instances_wc
 
 
-def make_level1_data(data, level0_commondata_wc, filterseed, experiments_index, sep_mult):
+def make_level1_data(data, level0_commondata_wc, filterseed, data_index, sep_mult):
     """
     Given a list of Level 0 commondata instances, return the
     same list with central values replaced by Level 1 data.
@@ -331,7 +331,7 @@ def make_level1_data(data, level0_commondata_wc, filterseed, experiments_index,
     filterseed : int
                 random seed used for the generation of Level 1 data
 
-    experiments_index : pandas.MultiIndex
+    data_index : pandas.MultiIndex
 
     Returns
     -------
@@ -367,7 +367,7 @@ def make_level1_data(data, level0_commondata_wc, filterseed, experiments_index,
         level0_commondata_wc, filterseed, covmat, sep_mult=sep_mult, genrep=True
     )
 
-    indexed_level1_data = indexed_make_replica(experiments_index, level1_data)
+    indexed_level1_data = indexed_make_replica(data_index, level1_data)
 
     dataset_order = {cd.setname: i for i, cd in enumerate(level0_commondata_wc)}