diff --git a/rmgpy/cantherm/gaussian.py b/rmgpy/cantherm/gaussian.py
index 8ec27939a2..4bab30b2f5 100644
--- a/rmgpy/cantherm/gaussian.py
+++ b/rmgpy/cantherm/gaussian.py
@@ -146,6 +146,8 @@ def loadGeometry(self):
                 mass[i] = 12.0
             elif number[i] == 8:
                 mass[i] = 15.99491461956
+            elif number[i] == 16:
+                mass[i] = 31.97207100
             else:
                 print 'Atomic number %i not yet supported in loadGeometry().' % number[i]