diff --git a/pyproject.toml b/pyproject.toml
index fa83393..d84a1f9 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -5,7 +5,7 @@ requires = [
 build-backend = "hatchling.build"
 [project]
 name = "itp_interface"
-version = "1.8.0"
+version = "1.9.0"
 authors = [
   { name="Amitayush Thakur", email="amitayush@utexas.edu" },
 ]
diff --git a/src/itp_interface/tools/isabelle_executor.py b/src/itp_interface/tools/isabelle_executor.py
index 5ba372a..9edec89 100644
--- a/src/itp_interface/tools/isabelle_executor.py
+++ b/src/itp_interface/tools/isabelle_executor.py
@@ -21,7 +21,7 @@
 try:
     from itp_interface.pisa.src.main.python.pisa_client import PisaEnv, initialise_env, IsabelleLemma
     HAS_ISABELLE = True
-except (ImportError, RuntimeError):
+except (ImportError, RuntimeError, TypeError):
     HAS_ISABELLE = False
     PisaEnv = None
     initialise_env = None