__iadd__ for Model broken about cobrapy HOT 2 CLOSED

Exception                                 Traceback (most recent call last)
<ipython-input-3-5ffb0b093e55> in <module>()
      5 model1 = cobra.io.read_sbml_model(cobra.test.salmonella_sbml)
      6 model = cobra.Model("test")
----> 7 model += model1

/home/aebrahim/cobrapy/cobra/core/Model.pyc in __iadd__(self, other_model)
     93         """
     94         new_reactions = deepcopy(other_model.reactions)
---> 95         self.add_reactions(new_reactions)
     96         self.id = self.id + '_' + other_model.id
     97         return self

/home/aebrahim/cobrapy/cobra/core/Model.pyc in add_reactions(self, reaction_list)
    244                 else:
    245                     model_gene = self.genes.get_by_id(gene.id)
--> 246                     reaction.remove_gene(gene)
    247                     reaction.add_gene(model_gene)
    248 

/home/aebrahim/cobrapy/cobra/core/Reaction.pyc in remove_gene(self, cobra_gene)
    554             cobra_gene._reaction.remove(self)
    555         except:
--> 556             raise Exception('Unable to remove gene %s from reaction %s.'%(cobra_gene.id, self.id))
    557 
    558     def add_gene(self, cobra_gene):

Exception: Unable to remove gene STM0999 from reaction 12PPDStex.