diff --git a/pymatgen/core/trajectory.py b/pymatgen/core/trajectory.py
index 1e365142285..962c5d374db 100644
--- a/pymatgen/core/trajectory.py
+++ b/pymatgen/core/trajectory.py
@@ -124,7 +124,7 @@ def __init__(
             if isinstance(lattice, Lattice):
                 lattice = lattice.matrix
             elif isinstance(lattice, list) and isinstance(lattice[0], Lattice):
-                lattice = [x.matrix for x in lattice]  # type: ignore
+                lattice = [cast(Lattice, x).matrix for x in lattice]
             lattice = np.asarray(lattice)
 
             if not constant_lattice and lattice.shape == (3, 3):