diff --git a/stl/stl2milp.py b/stl/stl2milp.py
index 920704c..097bb4d 100644
--- a/stl/stl2milp.py
+++ b/stl/stl2milp.py
@@ -53,7 +53,7 @@ def to_milp(self, formula, t=0):
             self.__milp_call[formula.op](formula, z, t)
         return z
 
-    def add_formula_variable(self, formula, t, vtype=grb.GRB.BINARY):
+    def add_formula_variable(self, formula, t):
         '''Adds a variable for the `formula` at time `t`.'''
         if formula not in self.variables:
             self.variables[formula] = dict()
@@ -61,10 +61,14 @@ def add_formula_variable(self, formula, t, vtype=grb.GRB.BINARY):
             opname = Operation.getString(formula.op)
             identifier = formula.identifier()
             name = '{}_{}_{}'.format(opname, identifier, t)
-            self.variables[formula][t] = self.model.addVar(vtype=vtype,
-                                                           name=name)
-            self.model.update() #TODO: not sure if this is needed (NEEDED!)
-            return self.variables[formula][t], True
+            if formula.op == Operation.PRED:
+                variable = self.model.addVar(vtype=grb.GRB.BINARY, name=name)
+            else:
+                variable = self.model.addVar(vtype=grb.GRB.CONTINUOUS,
+                                             name=name, lb=0, ub=1)
+            self.variables[formula][t] = variable
+            self.model.update()
+            return variable, True
         return self.variables[formula][t], False
 
     def add_state(self, state, t):
@@ -77,7 +81,6 @@ def add_state(self, state, t):
             name='{}_{}'.format(state, t)
             v = self.model.addVar(vtype=vtype, lb=low, ub=high, name=name)
             self.variables[state][t] = v
-            print 'Added state:', state, 'time:', t
             self.model.update()
         return self.variables[state][t]
 
@@ -173,4 +176,4 @@ def until(self, formula, z, t):
                                  + sum(z_children_left[:t+a+k+1]))
 
             self.model.addConstr(z >= z_conj)
-        self.model.addConstr(z <= sum(z_aux))
\ No newline at end of file
+        self.model.addConstr(z <= sum(z_aux))