diff --git a/lemon/lp_skeleton.cc b/lemon/lp_skeleton.cc
--- a/lemon/lp_skeleton.cc
+++ b/lemon/lp_skeleton.cc
@@ -2,7 +2,7 @@
  *
  * This file is a part of LEMON, a generic C++ optimization library.
  *
- * Copyright (C) 2003-2008
+ * Copyright (C) 2003-2010
  * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
  * (Egervary Research Group on Combinatorial Optimization, EGRES).
  *
@@ -32,6 +32,11 @@
     return ++row_num;
   }
 
+  int SkeletonSolverBase::_addRow(Value, ExprIterator, ExprIterator, Value)
+  {
+    return ++row_num;
+  }
+
   void SkeletonSolverBase::_eraseCol(int) {}
   void SkeletonSolverBase::_eraseRow(int) {}