diff --git a/mp_api/client/mprester.py b/mp_api/client/mprester.py
index 36f238cc7..f1c92f0ec 100644
--- a/mp_api/client/mprester.py
+++ b/mp_api/client/mprester.py
@@ -843,6 +843,8 @@ def get_ion_reference_data_for_chemsys(
         """
         ion_data = self.get_ion_reference_data()
 
+        if isinstance(chemsys, str):
+            chemsys = chemsys.split("-")
         return [d for d in ion_data if d["data"]["MajElements"] in chemsys]
 
     def get_ion_entries(
diff --git a/tests/test_mprester.py b/tests/test_mprester.py
index 64a46dfee..07f15b773 100644
--- a/tests/test_mprester.py
+++ b/tests/test_mprester.py
@@ -247,7 +247,11 @@ def test_get_ion_entries(self, mpr):
         ion_entry_data = mpr.get_ion_reference_data_for_chemsys("Ti-O-H")
         ion_entries = mpr.get_ion_entries(pd, ion_entry_data)
         assert len(ion_entries) == 5
-        assert all(isinstance(i, IonEntry) for i in ion_entries)
+        assert all([isinstance(i, IonEntry) for i in ion_entries])
+        bi_v_entry_data = mpr.get_ion_reference_data_for_chemsys("Bi-V")
+        bi_data = mpr.get_ion_reference_data_for_chemsys("Bi")
+        v_data = mpr.get_ion_reference_data_for_chemsys("V")
+        assert len(bi_v_entry_data) == len(bi_data) + v_data
 
         # test an incomplete phase diagram
         entries = mpr.get_entries_in_chemsys("Ti-O")