diff --git a/mfsetup/oc.py b/mfsetup/oc.py
index b913f7a2..34e16f83 100644
--- a/mfsetup/oc.py
+++ b/mfsetup/oc.py
@@ -29,6 +29,7 @@ def parse_oc_period_input(period_input, nstp=None, output_fmt='mf6'):
     """
     if nstp is not None:
         nstp = list(nstp)
+        nper = len(nstp)
 
     flopy_input = {}
     mf6_flopy_input = {}
@@ -64,6 +65,7 @@ def parse_oc_period_input(period_input, nstp=None, output_fmt='mf6'):
                                     raise ValueError("MODFLOW 2005-style OC input requires "
                                                         "timestep information.")
                                 # parse MF6-style instructions
+                                # into MF2005 style input
                                 kstp = 0
                                 nstep_idx = kper if kper < len(nstp) else -1
                                 instruction, *values = instruction
@@ -93,9 +95,9 @@ def parse_oc_period_input(period_input, nstp=None, output_fmt='mf6'):
                                 else:
                                     raise ValueError("mfsetup.oc.parse_oc: instruction "
                                                     f"'{instruction}' not understood")
-            if len(mf6_record_input) > 0:
+            if len(mf6_record_input) > 0 and output_fmt == 'mf6':
                 mf6_flopy_input[rec] = dict(mf6_record_input)
-            if len(mf_record_input) > 0:
+            elif len(mf_record_input) > 0:
                 mf_record_input = fill_oc_stress_period_data(mf_record_input, nper=len(nstp))
                 flopy_input['stress_period_data'] = dict(mf_record_input)
     if output_fmt == 'mf6':
diff --git a/mfsetup/tests/test_pfl_mfnwt_inset.py b/mfsetup/tests/test_pfl_mfnwt_inset.py
index c2c3fe3b..c223a052 100644
--- a/mfsetup/tests/test_pfl_mfnwt_inset.py
+++ b/mfsetup/tests/test_pfl_mfnwt_inset.py
@@ -529,12 +529,12 @@ def test_nwt_setup(pfl_nwt, project_root_path):
     ({'period_options': {0: ['save head last', 'save budget last'],
                          1: []}},
      {'stress_period_data': {(0, 0): ['save head', 'save budget'],
-                            (0, 1): []}}),
+                            (1, 0): []}}),
     # MODFLOW 2005-style input
     ({'stress_period_data': {(0, 0): ['save head', 'save budget'],
-                            (0, 1): []}},
+                            (1, 0): []}},
      {'stress_period_data': {(0, 0): ['save head', 'save budget'],
-                            (0, 1): []}})
+                            (1, 0): []}})
 ])
 def test_oc_setup(pfl_nwt, input, expected):
     m = pfl_nwt