diff --git a/dtls/openssl.py b/dtls/openssl.py
index bea985c..c48ea60 100644
--- a/dtls/openssl.py
+++ b/dtls/openssl.py
@@ -486,6 +486,7 @@ map(lambda x: _make_function(*x), (
     ("SSLeay_version", libcrypto, ((c_char_p, "ret"), (c_int, "t"))),
     ("CRYPTO_set_locking_callback", libcrypto,
      ((None, "ret"), (c_void_p, "func")), False),
+    ("CRYPTO_get_id_callback", libcrypto, ((c_void_p, "ret"),), True, None),
     ("CRYPTO_num_locks", libcrypto, ((c_int, "ret"),)),
     ("DTLSv1_server_method", libssl, ((DTLSv1Method, "ret"),)),
     ("DTLSv1_client_method", libssl, ((DTLSv1Method, "ret"),)),
diff --git a/dtls/tlock.py b/dtls/tlock.py
index 4aea6f8..1771dc1 100644
--- a/dtls/tlock.py
+++ b/dtls/tlock.py
@@ -21,6 +21,10 @@ DO_DEBUG_LOG = False
 def tlock_init():
     if not globals().has_key("threading"):
         return  # nothing to configure
+    # The standard library ssl module's lock implementation is more efficient;
+    # do not override it if it has been established
+    if CRYPTO_get_id_callback():
+        return
     global _locks
     num_locks = CRYPTO_num_locks()
     _locks = tuple(threading.Lock() for _ in range(num_locks))