diff --git a/bfps/cpp/rFFTW_interpolator.cpp b/bfps/cpp/rFFTW_interpolator.cpp
index 8310be04ca36714ed01d5facc5a4d973713de550..a858eb104abf19837f7ccd30ae673caaf841a493 100644
--- a/bfps/cpp/rFFTW_interpolator.cpp
+++ b/bfps/cpp/rFFTW_interpolator.cpp
@@ -51,7 +51,7 @@ rFFTW_interpolator<rnumber, interp_neighbours>::rFFTW_interpolator(
     this->compute = new bool[this->descriptor->sizes[0]];
     std::fill_n(this->compute, this->descriptor->sizes[0], false);
     for (int iz = this->descriptor->starts[0]-interp_neighbours-1;
-            iz <= this->descriptor->starts[0]+this->descriptor->subsizes[0]+interp_neighbours+1;
+            iz <= this->descriptor->starts[0]+this->descriptor->subsizes[0]+interp_neighbours;
             iz++)
         this->compute[((iz + this->descriptor->sizes[0]) % this->descriptor->sizes[0])] = true;
 }
diff --git a/tests/test_scaling.py b/tests/test_scaling.py
index 4acc554ef6af290fd488a7239ef7b17e1f4caaa1..a5e675ccc5fe3dccf1e41b4270591d681dceb9d9 100755
--- a/tests/test_scaling.py
+++ b/tests/test_scaling.py
@@ -54,8 +54,8 @@ if __name__ == '__main__':
             ['-n', '32',
              '--run',
              '--initialize',
-             '--ncpu', '2',
-             '--nparticles', '1000',
+             '--ncpu', '4',
+             '--nparticles', '10000',
              '--niter_todo', '32',
              '--precision', 'single',
              '--wd', 'data/single'] +