diff --git a/python/sdist/amici/de_export.py b/python/sdist/amici/de_export.py
index 6218642dd1..cf36fa441f 100644
--- a/python/sdist/amici/de_export.py
+++ b/python/sdist/amici/de_export.py
@@ -1662,8 +1662,8 @@ def static_indices(self, name: str) -> list[int]:
                         # splines: non-static
                         not self._splines or "AmiciSpline" not in str(expr)
                     )
-                    and smart_is_zero_matrix(
-                        smart_jacobian(sp.Matrix([expr]), dynamic_syms)
+                    and all(
+                        expr.diff(dyn_sym).is_zero for dyn_sym in dynamic_syms
                     )
                 )
             ]