diff --git a/pyparticles/forces/electromagnetic_field.py b/pyparticles/forces/electromagnetic_field.py
index 5e1b41f..c3c36f9 100644
--- a/pyparticles/forces/electromagnetic_field.py
+++ b/pyparticles/forces/electromagnetic_field.py
@@ -52,10 +52,10 @@ def __init__( self , size , dim=3 , m=None , q=None , Consts=1.0 ):
         
         self.__Cr = np.zeros( ( size , dim ) )
         
-        if m != None :
+        if m is not None :
             self.set_masses( m )
         
-        if q != None :
+        if q is not None :
             self.set_charges( q )
             
         self.__el_fields = dict()