diff --git a/pyproject.toml b/pyproject.toml
index 8421819e..91c9341f 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -41,6 +41,9 @@ hdf_reader = [
 icechunk = [
     "icechunk==0.1.0a8",
 ]
+kerchunk_readers = [
+    "astropy",
+]
 test = [
     "codecov",
     "fastparquet",
@@ -53,6 +56,7 @@ test = [
     "pandas-stubs",
     "pooch",
     "pre-commit",
+    "pytest-asyncio",
     "pytest-cov",
     "pytest-mypy",
     "pytest",
@@ -87,6 +91,10 @@ datatree = ["py.typed"]
 files = "virtualizarr/**/*.py"
 show_error_codes = true
 
+[[tool.mypy.overrides]]
+module = "astropy.*"
+ignore_missing_imports = true
+
 [[tool.mypy.overrides]]
 module = "fsspec.*"
 ignore_missing_imports = true
diff --git a/virtualizarr/readers/fits.py b/virtualizarr/readers/fits.py
index e9119ccb..b1ecbbd1 100644
--- a/virtualizarr/readers/fits.py
+++ b/virtualizarr/readers/fits.py
@@ -1,5 +1,5 @@
 from pathlib import Path
-from typing import Iterable, Mapping, Optional
+from typing import Any, Iterable, Mapping
 
 from xarray import Dataset, Index, Variable
 
@@ -23,10 +23,10 @@ def open_virtual_dataset(
         loadable_variables: Iterable[str] | None = None,
         decode_times: bool | None = None,
         indexes: Mapping[str, Index] | None = None,
-        virtual_backend_kwargs: Optional[dict] = None,
-        reader_options: Optional[dict] = None,
+        virtual_backend_kwargs: Mapping[str, Any] | None = None,
+        reader_options: Mapping[str, Any] | None = None,
     ) -> Dataset:
-        from kerchunk.fits import process_file
+        from virtualizarr.vendor.kerchunk.fits import process_file
 
         if virtual_backend_kwargs:
             raise NotImplementedError(
@@ -34,7 +34,9 @@ def open_virtual_dataset(
             )
 
         # handle inconsistency in kerchunk, see GH issue https://github.com/zarr-developers/VirtualiZarr/issues/160
-        refs = KerchunkStoreRefs({"refs": process_file(filepath, **reader_options)})
+        refs = KerchunkStoreRefs(
+            {"refs": process_file(filepath, **(reader_options or {}))}
+        )
 
         # both group=None and group='' mean to read root group
         if group:
diff --git a/virtualizarr/vendor/kerchunk/fits.py b/virtualizarr/vendor/kerchunk/fits.py
index 3ac93aac..2ae31052 100644
--- a/virtualizarr/vendor/kerchunk/fits.py
+++ b/virtualizarr/vendor/kerchunk/fits.py
@@ -10,13 +10,13 @@
 from virtualizarr.vendor.kerchunk.codecs import AsciiTableCodec, VarArrCodec
 
 try:
-    from astropy.io import fits
-    from astropy.wcs import WCS
+    from astropy.io import fits  # noqa: F401
+    from astropy.wcs import WCS  # noqa: F401
 except ModuleNotFoundError:  # pragma: no cover
     raise ImportError(
         "astropy is required for kerchunking FITS files. Please install with "
         "`pip/conda install astropy`."
-    )
+    ) from None
 
 logger = logging.getLogger("fits-to-zarr")
 
@@ -162,7 +162,12 @@ def process_file(
             # TODO: we could sub-chunk on biggest dimension
             name = hdu.name or str(ext)
             arr = g.empty(
-                name, dtype=dtype, shape=shape, chunks=shape, compression=None, **kwargs
+                name=name,
+                dtype=dtype,
+                shape=shape,
+                chunks=shape,
+                compression=None,
+                **kwargs,
             )
             arr.attrs.update(
                 {