diff --git a/src/if_python3.c b/src/if_python3.c
index ea59a42..e9f7400 100644
--- a/src/if_python3.c
+++ b/src/if_python3.c
@@ -731,8 +731,12 @@
 #else
 	PyMac_Initialize();
 #endif
-	/* initialise threads, must be after Py_Initialize() */
+	/* Initialise threads, and save the state using PyGILState_Ensure.
+	 * Without the call to PyGILState_Ensure, thread specific state (such
+	 * as the system trace hook), will be lost between invocations of
+	 * Python code. */
 	PyEval_InitThreads();
+	pygilstate = PyGILState_Ensure();
 
 #ifdef DYNAMIC_PYTHON3
 	get_py3_exceptions();