diff --git a/openmc/element.py b/openmc/element.py
index 66371aba9a..c391d08235 100644
--- a/openmc/element.py
+++ b/openmc/element.py
@@ -127,7 +127,7 @@ class Element(object):
 
         isotopes = []
         for isotope, abundance in natural_abundance.items():
-            if isotope.startswith(self.name):
+            if isotope.startswith(self.name + '-'):
                 nuc = openmc.Nuclide(isotope, self.xs)
                 isotopes.append((nuc, abundance))
         return isotopes