diff --git a/qupulse/pulses/parameters.py b/qupulse/pulses/parameters.py
index 5d181975f..b0cf065bc 100644
--- a/qupulse/pulses/parameters.py
+++ b/qupulse/pulses/parameters.py
@@ -187,7 +187,7 @@ def __init__(self, relation: Union[str, sympy.Expr]):
             self._expression = sympy.Eq(*sympy.sympify(relation.split('==')))
         else:
             self._expression = sympy.sympify(relation)
-        if not isinstance(self._expression, sympy.boolalg.Boolean):
+        if not isinstance(self._expression, sympy.logic.boolalg.Boolean):
             raise ValueError('Constraint is not boolean')
         self._expression = Expression(self._expression)