diff --git a/src/msspec/calculator.py b/src/msspec/calculator.py
index b4e6f70..2e32fc3 100644
--- a/src/msspec/calculator.py
+++ b/src/msspec/calculator.py
@@ -363,7 +363,30 @@ class _MSCALCULATOR(Calculator):
             for key, value in requirements.items():
                 setattr(self.spec_malloc_parameters, key, value)
             
-            do_spec(*requirements.values())
+            # cannot use this, unfortunately
+            #do_spec(*requirements.values())
+            do_spec(
+               requirements['NATP_M'],
+               requirements['NATCLU_M'],
+               requirements['NAT_EQ_M'],
+               requirements['N_CL_L_M'],
+               requirements['NE_M'],
+               requirements['NL_M'],
+               requirements['LI_M'],
+               requirements['NEMET_M'],
+               requirements['NO_ST_M'],
+               requirements['NDIF_M'],
+               requirements['NSO_M'],
+               requirements['NTEMP_M'],
+               requirements['NODES_EX_M'],
+               requirements['NSPIN_M'],
+               requirements['NTH_M'],
+               requirements['NPH_M'],
+               requirements['NDIM_M'],
+               requirements['N_TILT_M'],
+               requirements['N_ORD_M'],
+               requirements['NPATH_M'],
+               requirements['NGR_M'])
 
             t1 = time.time()
             self.resources['spec_time'] = t1 - t0