diff --git a/lemon/network_simplex.h b/lemon/network_simplex.h
--- a/lemon/network_simplex.h
+++ b/lemon/network_simplex.h
@@ -63,7 +63,8 @@
   /// \tparam C The number type used for costs and potentials in the
   /// algorithm. By default, it is the same as \c V.
   ///
-  /// \warning Both number types must be signed and all input data must
+  /// \warning Both \c V and \c C must be signed number types.
+  /// \warning All input data (capacities, supply values, and costs) must
   /// be integer.
   ///
   /// \note %NetworkSimplex provides five different pivot rule