diff --git a/pdbApp/pdbsingle.h b/pdbApp/pdbsingle.h
index 57e0fac..fff6312 100644
--- a/pdbApp/pdbsingle.h
+++ b/pdbApp/pdbsingle.h
@@ -125,7 +125,7 @@ struct PDBSingleMonitor : public BaseMonitor
 {
     POINTER_DEFINITIONS(PDBSingleMonitor);
 
-    PDBSinglePV::weak_pointer pv;
+    const PDBSinglePV::weak_pointer pv;
 
     static size_t num_instances;