diff --git a/src/common/configrules.cpp b/src/common/configrules.cpp
index 2eeca2649..d72608035 100644
--- a/src/common/configrules.cpp
+++ b/src/common/configrules.cpp
@@ -36,6 +36,9 @@ namespace cinelerra
     
     CINELERRA_ERROR_DEFINE (CAPABILITY_QUERY, "unresolvable capability query");
 
+    
+    ConfigRulesInterface<NullType>::~ConfigRulesInterface()
+      { };
   
   } // namespace query
     
diff --git a/src/common/configrules.hpp b/src/common/configrules.hpp
index 80ba8df3c..e17914187 100644
--- a/src/common/configrules.hpp
+++ b/src/common/configrules.hpp
@@ -118,9 +118,9 @@ namespace cinelerra
     class QueryHandler
       {
       protected:
-        virtual ~QueryHandler();
+        virtual ~QueryHandler()  { }
       public:
-        virtual shared_ptr<TY> resolve (Query<TY> q);
+        virtual shared_ptr<TY> resolve (Query<TY> q) = 0;
       };
 
     // TODO: the Idea is to provide specialisations for the concrete types
diff --git a/src/common/query/mockconfigrules.cpp b/src/common/query/mockconfigrules.cpp
index 915e20ba8..068f6bdbd 100644
--- a/src/common/query/mockconfigrules.cpp
+++ b/src/common/query/mockconfigrules.cpp
@@ -22,6 +22,12 @@
 
 
 #include "common/query/mockconfigrules.hpp"
+
+#include "proc/mobject/session/track.hpp"
+#include "proc/asset/procpatt.hpp"
+#include "proc/asset/port.hpp"
+
+
 //#include "common/util.hpp"
 #include "nobugcfg.h"
 
@@ -37,6 +43,24 @@ namespace cinelerra
     {
       
     }
+    
+    shared_ptr<Track> 
+    MockConfigRules::resolve (Query<Track> q)
+    {
+      UNIMPLEMENTED ("solve for Track");
+    }
+    
+    shared_ptr<Port>  
+    MockConfigRules::resolve (Query<Port> q)
+    {
+      UNIMPLEMENTED ("solve for Port");
+    }
+    
+    PProcPatt
+    MockConfigRules::resolve (Query<const ProcPatt> q)
+    {
+      UNIMPLEMENTED ("solve for ProcPatt");
+    }
 
   
   } // namespace query
diff --git a/src/common/query/mockconfigrules.hpp b/src/common/query/mockconfigrules.hpp
index 07fc98831..17f9b6f95 100644
--- a/src/common/query/mockconfigrules.hpp
+++ b/src/common/query/mockconfigrules.hpp
@@ -66,6 +66,8 @@ namespace cinelerra
       protected:
         MockConfigRules ();
         friend class cinelerra::singleton::StaticCreate<MockConfigRules>;
+
+        virtual ~MockConfigRules() {}
         
       public: