diff --git a/openmc/mgxs/mgxs.py b/openmc/mgxs/mgxs.py
index ca95be58ad..b79780ffc2 100644
--- a/openmc/mgxs/mgxs.py
+++ b/openmc/mgxs/mgxs.py
@@ -691,11 +691,11 @@ class MGXS(object):
         # Find, slice and store Tallies from StatePoint
         # The tally slicing is needed if tally merging was used
         for tally_type, tally in self.tallies.items():
-            sp_tally = statepoint.get_tally(tally.scores, tally.filters,
-                                            tally.nuclides,
-                                            estimator=tally.estimator)
-            sp_tally = sp_tally.get_slice(tally.scores, filters,
-                                          filter_bins, tally.nuclides)
+            sp_tally = statepoint.get_tally(
+                tally.scores, tally.filters, tally.nuclides,
+                estimator=tally.estimator, exact=True)
+            sp_tally = sp_tally.get_slice(
+                tally.scores, filters, filter_bins, tally.nuclides)
             sp_tally.sparse = self.sparse
             self.tallies[tally_type] = sp_tally
 
diff --git a/openmc/statepoint.py b/openmc/statepoint.py
index d5dd7bc1e7..83dd148fe7 100644
--- a/openmc/statepoint.py
+++ b/openmc/statepoint.py
@@ -497,13 +497,17 @@ class StatePoint(object):
                 self.tallies[tally_id].sparse = self.sparse
 
     def get_tally(self, scores=[], filters=[], nuclides=[],
-                  name=None, id=None, estimator=None):
+                  name=None, id=None, estimator=None, exact=False):
         """Finds and returns a Tally object with certain properties.
 
         This routine searches the list of Tallies and returns the first Tally
         found which satisfies all of the input parameters.
-        NOTE: The input parameters do not need to match the complete Tally
-        specification and may only represent a subset of the Tally's properties.
+
+        NOTE: If the "exact" parameter is False (default), the input parameters
+        do not need to match the complete Tally specification and may only
+        represent a subset of the Tally's properties. If the "exact" parameter
+        is True then the scores, filters, nuclides and estimator parameters
+        must precisely match those of any matching Tally.
 
         Parameters
         ----------
@@ -519,6 +523,9 @@ class StatePoint(object):
             The id specified for the Tally (default is None).
         estimator: str, optional
             The type of estimator ('tracklength', 'analog'; default is None).
+        exact : bool
+            Whether to strictly enforce the match between the parameters and
+            the returned tally
 
         Returns
         -------
@@ -547,9 +554,18 @@ class StatePoint(object):
                 continue
 
             # Determine if Tally has queried estimator
-            if estimator and not estimator == test_tally.estimator:
+            if (estimator or exact) and estimator != test_tally.estimator:
                 continue
 
+            # The number of filters, nuclides and scores must exactly match
+            if exact:
+                if len(scores) != test_tally.num_scores:
+                    continue
+                if len(nuclides) != test_tally.num_nuclides:
+                    continue
+                if len(filters) != test_tally.num_filters:
+                    continue
+
             # Determine if Tally has the queried score(s)
             if scores:
                 contains_scores = True