diff --git a/src/diffraxtra/interp.py b/src/diffraxtra/interp.py
index 77b51ad..4329807 100644
--- a/src/diffraxtra/interp.py
+++ b/src/diffraxtra/interp.py
@@ -420,7 +420,7 @@ def apply_to_solution(cls, soln: dfx.Solution, /) -> dfx.Solution:
         in a `VectorizedDenseInterpolation`.
 
         """
-        if soln.interpolation is None:
+        if soln.interpolation is None or isinstance(soln.interpolation, cls):  # type: ignore[unreachable]
             return soln
 
         vec_soln: dfx.Solution = eqx.tree_at(