diff --git a/src/pygom/model/base_ode_model.py b/src/pygom/model/base_ode_model.py
index 379043e5..eac60baf 100644
--- a/src/pygom/model/base_ode_model.py
+++ b/src/pygom/model/base_ode_model.py
@@ -163,6 +163,8 @@ def parameters(self):
             (:mod:`sympy.core.symbol`, numeric)
 
         """
+        if not hasattr(self, "_parameters"):
+            return None
         return self._parameters
 
     @parameters.setter
@@ -1500,4 +1502,4 @@ def _extractUpperTriangle(self, A, nrow=None, ncol=None):
             for j in range(i, ncol):
                 B[i,j] = A[i, j]
 
-        return B
\ No newline at end of file
+        return B