--- a/src/query/docseq.cpp
+++ b/src/query/docseq.cpp
@@ -22,7 +22,7 @@
 #include "log.h"
 #include "internfile.h"
 
-PTMutexInit DocSequence::o_dblock;
+std::mutex DocSequence::o_dblock;
 string DocSequence::o_sort_trans;
 string DocSequence::o_filt_trans;
 
@@ -46,7 +46,7 @@
 	LOGERR("DocSequence::getEnclosing: no db\n" );
 	return false;
     }
-    PTMutexLocker locker(o_dblock);
+    std::unique_lock<std::mutex> locker(o_dblock);
     string udi;
     if (!FileInterner::getEnclosingUDI(doc, udi))
         return false;