diff --git a/hmatrix-glpk.cabal b/hmatrix-glpk.cabal
--- a/hmatrix-glpk.cabal
+++ b/hmatrix-glpk.cabal
@@ -1,5 +1,5 @@
 Name:               hmatrix-glpk
-Version:            0.4.0.1
+Version:            0.4.0.2
 License:            GPL
 License-file:       LICENSE
 Author:             Alberto Ruiz
diff --git a/src/Numeric/LinearProgramming.hs b/src/Numeric/LinearProgramming.hs
--- a/src/Numeric/LinearProgramming.hs
+++ b/src/Numeric/LinearProgramming.hs
@@ -17,7 +17,8 @@
 subject to
 
 2 x_1 +   x_2 <= 10
-  x_3 + 5 x_4 <= 20
+
+  x_2 + 5 x_3 <= 20
 
 and