diff --git a/tests/lbpm_serial_decomp.cpp b/tests/lbpm_serial_decomp.cpp
index 46431c37..da016fb1 100644
--- a/tests/lbpm_serial_decomp.cpp
+++ b/tests/lbpm_serial_decomp.cpp
@@ -168,6 +168,10 @@ int main(int argc, char **argv)
 								int64_t y = yStart + jp*ny + j-1;
 								// int64_t z = zStart + kp*nz + k-1;
 								int64_t z = zStart + kp*nz + k-1 - z_transition_size;
+								if (x<xStart) 	x=xStart;
+								if (!(x<Nx))	x=Nx-1;
+								if (y<yStart) 	y=yStart;
+								if (!(y<Ny))	y=Ny-1;
 								if (z<zStart) 	z=zStart;
 								if (!(z<Nz))	z=Nz-1;
 								int64_t nlocal = k*(nx+2)*(ny+2) + j*(nx+2) + i;