diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 7bf48a0..8f6c0c7 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -1,5 +1,8 @@
 name: ci
 
+env:
+  CMAKE_BUILD_TYPE: Release
+
 on:
   push:
     paths:
@@ -37,8 +40,8 @@ jobs:
 
     - run: pytest
       env:
-        FC: gfortran-10
-        CC: gcc-10
+        FC: gfortran-11
+        CC: gcc-11
 
   windows:
     needs: linux
diff --git a/pyproject.toml b/pyproject.toml
index a3e8a88..90ccf9c 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -3,6 +3,3 @@ requires = ["setuptools", "wheel"]
 
 [tool.black]
 line-length = 100
-
-[tool.pytest.ini_options]
-addopts = "-ra -v"
diff --git a/setup.cfg b/setup.cfg
index e4f06de..1017768 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -1,6 +1,6 @@
 [metadata]
 name = igrf
-version = 13.0.0
+version = 13.0.1
 author = Michael Hirsch, Ph.D.
 author_email = scivision@users.noreply.github.com
 description = IGRF13, IGRF12, IGRF11 models with simple object-oriented Python interface.
@@ -44,6 +44,7 @@ lint =
   flake8-builtins
   flake8-blind-except
   mypy
+  types-python-dateutil
 plot =
   matplotlib
 
diff --git a/src/igrf/CMakeLists.txt b/src/igrf/CMakeLists.txt
index 5704cf3..3a2f180 100644
--- a/src/igrf/CMakeLists.txt
+++ b/src/igrf/CMakeLists.txt
@@ -1,8 +1,7 @@
-cmake_minimum_required(VERSION 3.12)
-if(NOT CMAKE_BUILD_TYPE)
-  set(CMAKE_BUILD_TYPE Release CACHE STRING "Debug or Release")
-endif()
+cmake_minimum_required(VERSION 3.14...3.21)
+
 project(igrf LANGUAGES Fortran)
+
 enable_testing()
 
 add_executable(igrf13_driver fortran/igrf13_driver.f90 fortran/igrf13.f)
diff --git a/src/igrf/base.py b/src/igrf/base.py
index d663627..c39272a 100644
--- a/src/igrf/base.py
+++ b/src/igrf/base.py
@@ -90,7 +90,13 @@ def grid(
 
 
 def igrf(
-    time: datetime, glat: float, glon: float, alt_km: np.ndarray, *, isv: int = 0, itype: int = 1,
+    time: datetime,
+    glat: float,
+    glon: float,
+    alt_km: np.ndarray,
+    *,
+    isv: int = 0,
+    itype: int = 1,
 ) -> xarray.Dataset:
     """
 
@@ -139,7 +145,7 @@ def igrf(
         attrs={"time": time, "isv": isv, "itype": itype, "glat": glat, "glon": glon},
     )
 
-    decl, incl = mag_vector2incl_decl(mag.north, mag.east, mag.down)
+    decl, incl = mag_vector2incl_decl(mag.north.data, mag.east.data, mag.down.data)
 
     mag["incl"] = ("alt_km", incl)
     mag["decl"] = ("alt_km", decl)
diff --git a/src/igrf/utils.py b/src/igrf/utils.py
index f291e25..3649ca4 100644
--- a/src/igrf/utils.py
+++ b/src/igrf/utils.py
@@ -1,11 +1,11 @@
-import typing
+from __future__ import annotations
 import datetime
 from dateutil.parser import parse
 import numpy as np
 
 
 # %% utility functions
-def mag_vector2incl_decl(x: float, y: float, z: float) -> typing.Tuple[float, float]:
+def mag_vector2incl_decl(x: float, y: float, z: float) -> tuple[float, float]:
     """
     Inputs:
     -------
@@ -29,7 +29,7 @@ def mag_vector2incl_decl(x: float, y: float, z: float) -> typing.Tuple[float, fl
     return decl, incl
 
 
-def latlon2colat(glat: float, glon: float) -> typing.Tuple[np.ndarray, np.ndarray]:
+def latlon2colat(glat: float, glon: float) -> tuple[np.ndarray, np.ndarray]:
     # atleast_1d for iteration later
     colat = 90 - np.atleast_1d(glat)
     elon = (360 + np.atleast_1d(glon)) % 360
@@ -37,7 +37,7 @@ def latlon2colat(glat: float, glon: float) -> typing.Tuple[np.ndarray, np.ndarra
     return colat, elon
 
 
-def latlonworldgrid(latstep: int = 5, lonstep: int = 5) -> typing.Tuple[np.ndarray, np.ndarray]:
+def latlonworldgrid(latstep: int = 5, lonstep: int = 5) -> tuple[np.ndarray, np.ndarray]:
     lat = np.arange(-90.0, 90 + latstep, latstep)
     lon = np.arange(-180.0, 180 + lonstep, lonstep)
     glon, glat = np.meshgrid(lon, lat)
@@ -45,7 +45,7 @@ def latlonworldgrid(latstep: int = 5, lonstep: int = 5) -> typing.Tuple[np.ndarr
     return glat, glon
 
 
-def datetime2yeardec(time: typing.Union[str, datetime.datetime, datetime.date]) -> float:
+def datetime2yeardec(time: str | datetime.datetime | datetime.date) -> float:
     """
     Convert a datetime into a float. The integer part of the float should
     represent the year.