diff --git a/Modules/bz2module.c b/Modules/bz2module.c
index 5f1d01b..550f1cf 100644
--- a/Modules/bz2module.c
+++ b/Modules/bz2module.c
@@ -78,7 +78,12 @@
 
 
 #ifdef WITH_THREAD
-#define ACQUIRE_LOCK(obj) PyThread_acquire_lock(obj->lock, 1)
+#define ACQUIRE_LOCK(obj) do { \
+	if (!PyThread_acquire_lock(obj->lock, 0)) { \
+		Py_BEGIN_ALLOW_THREADS \
+		PyThread_acquire_lock(obj->lock, 1); \
+		Py_END_ALLOW_THREADS \
+	} } while(0)
 #define RELEASE_LOCK(obj) PyThread_release_lock(obj->lock)
 #else
 #define ACQUIRE_LOCK(obj)