diff --git a/bfps/cpp/fftw_tools.cpp b/bfps/cpp/fftw_tools.cpp
index c9e685268c1fda92881798670933ca0c455f6420..f6eacbf1dfe2dfe31e603e9239c42d4639327d3d 100644
--- a/bfps/cpp/fftw_tools.cpp
+++ b/bfps/cpp/fftw_tools.cpp
@@ -28,9 +28,7 @@
 #include "base.hpp"
 #include "fftw_tools.hpp"
 
-//#ifdef NDEBUG
-//#undef NDEBUG
-//#endif//NDEBUG
+#define NDEBUG
 
 template <class rnumber>
 int clip_zero_padding(
diff --git a/bfps/cpp/field_descriptor.cpp b/bfps/cpp/field_descriptor.cpp
index 87f25a169accb92d185cbda8dbed4753846cba14..b5025835903a37ea5384cb4102c716f527aabfe5 100644
--- a/bfps/cpp/field_descriptor.cpp
+++ b/bfps/cpp/field_descriptor.cpp
@@ -22,10 +22,9 @@
 *                                                                     *
 **********************************************************************/
 
-// code is generally compiled via setuptools, therefore NDEBUG is present
-//#ifdef NDEBUG
-//#undef NDEBUG
-//#endif//NDEBUG
+
+
+#define NDEBUG
 
 #include <stdlib.h>
 #include <algorithm>
diff --git a/bfps/cpp/fluid_solver.cpp b/bfps/cpp/fluid_solver.cpp
index 04b4aa5a1c88ee40bc70b0ad62b88f6d35935280..880d4f695fc513ddd6d4d931bf08ff83e2a5f5d6 100644
--- a/bfps/cpp/fluid_solver.cpp
+++ b/bfps/cpp/fluid_solver.cpp
@@ -22,10 +22,9 @@
 *                                                                     *
 **********************************************************************/
 
-// code is generally compiled via setuptools, therefore NDEBUG is present
-//#ifdef NDEBUG
-//#undef NDEBUG
-//#endif//NDEBUG
+
+
+#define NDEBUG
 
 #include <cassert>
 #include <cmath>
diff --git a/bfps/cpp/fluid_solver_base.cpp b/bfps/cpp/fluid_solver_base.cpp
index d570f80f98d3be1a990c56592b192fc97478e21a..7f191f88da6cee5bfbd23b423e5b956dd2a3906a 100644
--- a/bfps/cpp/fluid_solver_base.cpp
+++ b/bfps/cpp/fluid_solver_base.cpp
@@ -22,10 +22,9 @@
 *                                                                     *
 **********************************************************************/
 
-// code is generally compiled via setuptools, therefore NDEBUG is present
-//#ifdef NDEBUG
-//#undef NDEBUG
-//#endif//NDEBUG
+
+
+#define NDEBUG
 
 #include <cassert>
 #include <cmath>
diff --git a/bfps/cpp/slab_field_particles.cpp b/bfps/cpp/slab_field_particles.cpp
index 3988659a0caba5eb46fd2070b178f68a5694a343..15fa363f6d277d34c6081fd545c4578e1f735929 100644
--- a/bfps/cpp/slab_field_particles.cpp
+++ b/bfps/cpp/slab_field_particles.cpp
@@ -22,10 +22,9 @@
 *                                                                     *
 **********************************************************************/
 
-// code is generally compiled via setuptools, therefore NDEBUG is present
-//#ifdef NDEBUG
-//#undef NDEBUG
-//#endif//NDEBUG
+
+
+#define NDEBUG
 
 
 #include <cmath>
diff --git a/bfps/cpp/tracers.cpp b/bfps/cpp/tracers.cpp
index 5e0e106ea658741fdf1b1bb209e100b22474504c..3d9fbfb6a1e357d70452466b6cc901659444539d 100644
--- a/bfps/cpp/tracers.cpp
+++ b/bfps/cpp/tracers.cpp
@@ -22,10 +22,9 @@
 *                                                                     *
 **********************************************************************/
 
-// code is generally compiled via setuptools, therefore NDEBUG is present
-//#ifdef NDEBUG
-//#undef NDEBUG
-//#endif//NDEBUG
+
+
+#define NDEBUG
 
 
 #include <cmath>
diff --git a/tox_convergence.ini b/tox_convergence.ini
index 447e32fe9a7ffa2fc7adbcd9e07ca464785b8700..39a368ff0d1954cb841cbaab41e5a8d98bb68031 100644
--- a/tox_convergence.ini
+++ b/tox_convergence.ini
@@ -1,6 +1,7 @@
 [tox]
-envlist = py27
+envlist = py34
 [testenv]
+deps = matplotlib
 whitelist_externals =
     echo
     cp