diff --git a/include/GooseFEM/config.h b/include/GooseFEM/config.h
index 8d56051..f4a4da4 100644
--- a/include/GooseFEM/config.h
+++ b/include/GooseFEM/config.h
@@ -1,77 +1,85 @@
 /*
 
 (c - GPLv3) T.W.J. de Geus (Tom) | tom@geus.me | www.geus.me | github.com/tdegeus/GooseFEM
 
 */
 
 #ifndef GOOSEFEM_CONFIG_H
 #define GOOSEFEM_CONFIG_H
 
 #define _USE_MATH_DEFINES // to use "M_PI" from "math.h"
 
 #include <algorithm>
 #include <assert.h>
 #include <cstdlib>
 #include <iomanip>
 #include <iostream>
 #include <limits>
 #include <math.h>
 #include <memory>
 #include <numeric>
 #include <string>
 #include <vector>
 
 #include <xtensor/xadapt.hpp>
 #include <xtensor/xarray.hpp>
 #include <xtensor/xfixed.hpp>
 #include <xtensor/xinfo.hpp>
 #include <xtensor/xio.hpp>
 #include <xtensor/xlayout.hpp>
 #include <xtensor/xmath.hpp>
 #include <xtensor/xnoalias.hpp>
 #include <xtensor/xsort.hpp>
 #include <xtensor/xshape.hpp>
 #include <xtensor/xstrided_view.hpp>
 #include <xtensor/xtensor.hpp>
 #include <xtensor/xutils.hpp>
 #include <xtensor/xview.hpp>
 
 using namespace xt::placeholders;
 
 #define UNUSED(p) ((void)(p))
 
 #ifdef GOOSEFEM_ENABLE_ASSERT
 #define GOOSEFEM_ASSERT(expr) GOOSEFEM_ASSERT_IMPL(expr, __FILE__, __LINE__)
 #define GOOSEFEM_ASSERT_IMPL(expr, file, line) \
     if (!(expr)) { \
         throw std::runtime_error( \
             std::string(file) + ':' + std::to_string(line) + \
             ": assertion failed (" #expr ") \n\t"); \
     }
 #else
 #define GOOSEFEM_ASSERT(expr)
 #endif
 
 #define GOOSEFEM_CHECK(expr) GOOSEFEM_CHECK_IMPL(expr, __FILE__, __LINE__)
 #define GOOSEFEM_CHECK_IMPL(expr, file, line) \
     if (!(expr)) { \
         throw std::runtime_error( \
             std::string(file) + ':' + std::to_string(line) + \
             ": assertion failed (" #expr ") \n\t"); \
     }
 
+#define GOOSEFEM_WIP_ASSERT(expr) GOOSEFEM_CHECK_IMPL(expr, __FILE__, __LINE__)
+#define GOOSEFEM_WIP_ASSERT_IMPL(expr, file, line) \
+    if (!(expr)) { \
+        throw std::runtime_error( \
+            std::string(file) + ':' + std::to_string(line) + \
+            ": WIP, please extend the code, assertion failed (" #expr ") \n\t"); \
+    }
+
 #define GOOSEFEM_VERSION_MAJOR 0
 #define GOOSEFEM_VERSION_MINOR 5
 #define GOOSEFEM_VERSION_PATCH 1
 
 #define GOOSEFEM_VERSION_AT_LEAST(x, y, z) \
     (GOOSEFEM_VERSION_MAJOR > x || (GOOSEFEM_VERSION_MAJOR >= x && \
     (GOOSEFEM_VERSION_MINOR > y || (GOOSEFEM_VERSION_MINOR >= y && \
                                     GOOSEFEM_VERSION_PATCH >= z))))
 
 #define GOOSEFEM_VERSION(x, y, z) \
     (GOOSEFEM_VERSION_MAJOR == x && \
      GOOSEFEM_VERSION_MINOR == y && \
      GOOSEFEM_VERSION_PATCH == z)
 
 #endif