diff --git a/salamanca/models/project.py b/salamanca/models/project.py
index eeca59e..42de91e 100644
--- a/salamanca/models/project.py
+++ b/salamanca/models/project.py
@@ -453,10 +453,13 @@ def construct(self, diffusion={}, direction={}, spread={}, threshold=1.0):
         )
         m = self.model
         # Constraints specific to this model
-        m.cdf_lo = mo.Constraint(rule=threshold_lo_rule,
-                                 doc='Population under threshold within 5%')
-        m.cdf_hi = mo.Constraint(rule=threshold_hi_rule,
-                                 doc='Population under threshold within 5%')
+
+        m.cdf_lo = mo.Constraint(
+            rule=lambda m: threshold_lo_rule(m, f=threshold),
+            doc='Population under threshold within 5%')
+        m.cdf_hi = mo.Constraint(
+            rule=lambda m: threshold_hi_rule(m, f=threshold),
+            doc='Population under threshold within 5%')
         # Objective
         m.obj = mo.Objective(rule=theil_total_sum_obj, sense=mo.minimize)
         return self