diff --git a/pubchempy.py b/pubchempy.py
index 8de112f..7bfa4a3 100644
--- a/pubchempy.py
+++ b/pubchempy.py
@@ -560,7 +560,7 @@ def to_dict(self):
         for coord in {'x', 'y', 'z'}:
             if getattr(self, coord) is not None:
                 data[coord] = getattr(self, coord)
-        if self.charge is not 0:
+        if self.charge != 0:
             data['charge'] = self.charge
         return data