diff --git a/goatools/__init__.py b/goatools/__init__.py
index 1da4e38..3a332cd 100644
--- a/goatools/__init__.py
+++ b/goatools/__init__.py
@@ -1,23 +1,23 @@
 from datetime import datetime
-from pkg_resources import get_distribution, DistributionNotFound
+from importlib.metadata import version, PackageNotFoundError
 
 __author__ = ("Haibao Tang", "DV Klopfenstein")
-__copyright__ = "Copyright (C) 2009-{}, Haibao Tang, DV Klopfenstein".format(
-    datetime.now().year
+__copyright__ = (
+    f"Copyright (C) 2009-{datetime.now().year}, Haibao Tang, DV Klopfenstein"
 )
 __email__ = "tanghaibao@gmail.com"
 __license__ = "BSD"
 __status__ = "Development"
 
 try:
-    VERSION = get_distribution(__name__).version
-except DistributionNotFound:  # pragma: no cover
+    VERSION = version(__name__)
+except PackageNotFoundError:  # pragma: no cover
     try:
         from .version import version as VERSION  # noqa
-    except ImportError:  # pragma: no cover
+    except ImportError as exc:  # pragma: no cover
         raise ImportError(
             "Failed to find (autogenerated) version.py. "
             "This might be because you are installing from GitHub's tarballs, "
             "use the PyPI ones."
-        )
+        ) from exc
 __version__ = VERSION
diff --git a/tests/test_i304_regulates.py b/tests/test_i304_regulates.py
new file mode 100644
index 0000000..1ea0389
--- /dev/null
+++ b/tests/test_i304_regulates.py
@@ -0,0 +1,15 @@
+from goatools.gosubdag.gosubdag import GoSubDag
+from goatools.obo_parser import GODag
+
+
+def test_i304_regulates():
+    godag = GODag("go-basic.obo", optional_attrs=["relationship"])
+    optional_relationships = {
+        "regulates",
+        "negatively_regulates",
+        "positively_regulates",
+    }
+    anc = GoSubDag(
+        ["GO:0019222"], godag, optional_relationships, prt=None
+    ).rcntobj.go2ancestors["GO:0019222"]
+    assert len(anc) == 4