diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 0305d88..52be444 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -26,7 +26,7 @@ jobs:
     - name: Setup Apptainer
       uses: eWaterCycle/setup-apptainer@v2
       with:
-        apptainer-version: 1.1.3
+        apptainer-version: 1.1.9
     - name: Pull Docker image
       run: docker pull ewatercycle/walrus-grpc4bmi:v0.3.1
     - name: Cache Apptainer image
diff --git a/grpc4bmi/bmi_grpc_client.py b/grpc4bmi/bmi_grpc_client.py
index 2db4cfe..b16243f 100644
--- a/grpc4bmi/bmi_grpc_client.py
+++ b/grpc4bmi/bmi_grpc_client.py
@@ -9,7 +9,6 @@
 from bmipy import Bmi
 import grpc
 import numpy
-from typeguard import typechecked
 
 from grpc_status import rpc_status
 from google.rpc import error_details_pb2
@@ -94,7 +93,6 @@ def get_unique_port(host=None):
             s.bind(("" if host is None else host, 0))
             return int(s.getsockname()[1])
 
-    @typechecked
     def initialize(self, filename: Optional[str]):
         fname = "" if filename is None else filename
         try:
diff --git a/test/test_client.py b/test/test_client.py
index 26419a4..9017f2a 100644
--- a/test/test_client.py
+++ b/test/test_client.py
@@ -9,7 +9,6 @@
 from google.rpc import error_details_pb2, status_pb2, code_pb2
 from grpc_status import rpc_status
 from heat import BmiHeat
-from typeguard import TypeCheckError
 
 from grpc4bmi.bmi_grpc_server import BmiServer
 from grpc4bmi.bmi_grpc_client import BmiClient, RemoteException, handle_error
@@ -109,7 +108,7 @@ def test_initialize():
 def test_initialize_with_nonstring():
     client, local = make_bmi_classes(False)
     assert client is not None
-    with pytest.raises(TypeCheckError, match='did not match any element in the union'):
+    with pytest.raises(TypeError, match='bad argument type for built-in operation'):
         client.initialize(42)
     client.finalize()
     del client