diff --git a/tardis/opacities/opacity_solver.py b/tardis/opacities/opacity_solver.py
index 9b3b63f48ad..d5e821b99a7 100644
--- a/tardis/opacities/opacity_solver.py
+++ b/tardis/opacities/opacity_solver.py
@@ -46,7 +46,9 @@ def solve(self, legacy_plasma) -> OpacityState:
                         legacy_plasma.atomic_data.lines.shape[
                             0
                         ],  # number of lines
-                        legacy_plasma.abundance.shape[1],  # number of shells
+                        legacy_plasma.number_density.shape[
+                            1
+                        ],  # number of shells
                     ),
                     dtype=np.float64,
                 ),