diff --git a/python/sdist/amici/sbml_import.py b/python/sdist/amici/sbml_import.py
index 61cb79043e..55d6dad903 100644
--- a/python/sdist/amici/sbml_import.py
+++ b/python/sdist/amici/sbml_import.py
@@ -1143,7 +1143,12 @@ def _process_parameters(
 
         # parameter ID => initial assignment sympy expression
         par_id_to_ia = {
-            par.getId(): ia
+            par.getId(): ia.subs(
+                {
+                    BooleanTrue(): sp.Float(1.0),
+                    BooleanFalse(): sp.Float(0.0),
+                }
+            ).evalf()
             for par in self.sbml.getListOfParameters()
             if (ia := self._get_element_initial_assignment(par.getId()))
             is not None