diff --git a/audio/transport.c b/audio/transport.c
index 934bf37..281895e 100644
--- a/audio/transport.c
+++ b/audio/transport.c
@@ -807,6 +807,10 @@ static DBusMessage *acquire(DBusConnection *conn, DBusMessage *msg,
 	if (lock == 0)
 		return btd_error_invalid_args(msg);
 
+	if (transport->state != TRANSPORT_STATE_PENDING &&
+				g_strstr_len(accesstype, -1, "?") != NULL)
+		return btd_error_failed(msg, "Transport not playing");
+
 	if (media_transport_acquire(transport, lock) == FALSE)
 		return btd_error_not_authorized(msg);
 
diff --git a/doc/media-api.txt b/doc/media-api.txt
index da8ef53..b9802d9 100644
--- a/doc/media-api.txt
+++ b/doc/media-api.txt
@@ -282,6 +282,17 @@ Methods		dict GetProperties()
 
 				"rw": Read and write access
 
+			The accesstype string can also be combined with a "?"
+			suffix, which will make the request optional. This
+			typically means the transport will only be acquired if
+			it is already available (remote-initiated), but
+			otherwise no request will be sent to the remote side.
+			In this last case the function will fail. Note that,
+			due to compatibility issues with older versions of
+			BlueZ, clients are encouraged to use exactly the same
+			accesstype for Release(), matching the string provided
+			to Acquire().
+
 		void Release(string accesstype)
 
 			Releases file descriptor.