diff -r 774349a16ba0 -r 1fe3b4ad8caa lemon/concepts/graph_components.h
--- a/lemon/concepts/graph_components.h	Wed Nov 07 18:13:26 2012 +0100
+++ b/lemon/concepts/graph_components.h	Wed Nov 28 12:02:36 2012 +0100
@@ -108,6 +108,8 @@
           i1 = i2 = i3;
 
           bool b;
+          ignore_unused_variable_warning(b);
+
           b = (ia == ib) && (ia != ib);
           b = (ia == INVALID) && (ib != INVALID);
           b = (ia < ib);