diff --git a/Modules/_testcapimodule.c b/Modules/_testcapimodule.c
index edfe8ad..b11f0ae 100644
--- a/Modules/_testcapimodule.c
+++ b/Modules/_testcapimodule.c
@@ -667,6 +667,9 @@
 	PyThread_acquire_lock(thread_done, 1);  /* wait for thread to finish */
 	Py_END_ALLOW_THREADS
 
+	/* Release lock we acquired above.  This is required on HP-UX. */
+	PyThread_release_lock(thread_done);
+
 	PyThread_free_lock(thread_done);
 	Py_RETURN_NONE;
 }