diff --git a/openmc/deplete/results.py b/openmc/deplete/results.py
index d9e4673225..2e537a1b73 100644
--- a/openmc/deplete/results.py
+++ b/openmc/deplete/results.py
@@ -318,7 +318,7 @@ class Results(list):
             # Divide by volume to get density
             mass /= self[0].volume[mat_id]
         elif mass_units == "kg":
-            mass *= 1e3
+            mass /= 1e3
 
         return times, mass
 
diff --git a/tests/unit_tests/test_deplete_resultslist.py b/tests/unit_tests/test_deplete_resultslist.py
index 190affea99..b22a786509 100644
--- a/tests/unit_tests/test_deplete_resultslist.py
+++ b/tests/unit_tests/test_deplete_resultslist.py
@@ -111,7 +111,7 @@ def test_get_mass(res):
     assert n_cm3 == pytest.approx(n_ref / volume)
 
     t_min, n_bcm = res.get_mass("1", "Xe135", mass_units="kg", time_units="min")
-    assert n_bcm == pytest.approx(n_ref * 1e3)
+    assert n_bcm == pytest.approx(n_ref / 1e3)
     assert t_min == pytest.approx(t_ref / 60)
 
     t_hour, _n = res.get_mass("1", "Xe135", time_units="h")