diff --git a/.github/workflows/mypy.yml b/.github/workflows/mypy.yml
index 083d041ce..7750e59cf 100644
--- a/.github/workflows/mypy.yml
+++ b/.github/workflows/mypy.yml
@@ -16,7 +16,7 @@ jobs:
   mypy:
     strategy:
       matrix:
-        python-version: ["3.9", "3.12"]
+        python-version: ["3.8", "3.11"]
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
diff --git a/src/xtgeo/grid3d/_grid_etc1.py b/src/xtgeo/grid3d/_grid_etc1.py
index 1f00cfe8e..50f80289c 100644
--- a/src/xtgeo/grid3d/_grid_etc1.py
+++ b/src/xtgeo/grid3d/_grid_etc1.py
@@ -5,7 +5,7 @@
 from copy import deepcopy
 from functools import lru_cache
 from math import atan2, degrees
-from typing import TYPE_CHECKING, Literal
+from typing import TYPE_CHECKING, Literal, no_type_check
 
 import numpy as np
 import pandas as pd
@@ -1007,6 +1007,7 @@ def copy(self: Grid) -> Grid:
     )
 
 
+@no_type_check
 def crop(
     self: Grid,
     spec: tuple[tuple[int, int], tuple[int, int], tuple[int, int]],
@@ -1100,7 +1101,7 @@ def crop(
             if arrxmap.size > 0:
                 newsub[sub] = arrxmap.astype(np.int32).tolist()
 
-        self.subgrids = newsub  # type: ignore[cryptical mypy error]
+        self.subgrids = newsub
 
     # crop properties
     props = self.props if props == "all" else props