diff --git a/HISTORY b/HISTORY
index 645c8b3..3f394b8 100644
--- a/HISTORY
+++ b/HISTORY
@@ -1,6 +1,7 @@
 VDR Plugin 'streamdev' Revision History
 ---------------------------------------
  
+- client compatibility with VDR 2.3.1
 - use cReceiver::SetPriority(...) in VDR 2.1.4+
 - doubled size of client's filter buffer (suggested by Toerless Eckert)
 - make sure TimedWrite(...) doesn't return failure after a slow but successful
diff --git a/client/filter.c b/client/filter.c
index 94640d2..ffefa47 100644
--- a/client/filter.c
+++ b/client/filter.c
@@ -219,9 +219,8 @@ int cStreamdevFilters::OpenFilter(u_short Pid, u_char Tid, u_char Mask) {
 	cStreamdevFilter *f = new cStreamdevFilter(Pid, Tid, Mask);
 	int fh = f->ReadPipe();
 
-	Lock();
+	LOCK_THREAD;
 	Add(f);
-	Unlock();
 
 	return fh;
 }