diff --git a/src/HYMLS_CartesianPartitioner.cpp b/src/HYMLS_CartesianPartitioner.cpp
index e25eca20..398817ec 100644
--- a/src/HYMLS_CartesianPartitioner.cpp
+++ b/src/HYMLS_CartesianPartitioner.cpp
@@ -267,6 +267,9 @@ int CartesianPartitioner::GetGroups(int sd, Teuchos::Array<hymls_gidx> &interior
   int ymax = std::min(ny_ - ypos - 1, sy_ - 1);
   int zmax = std::min(nz_ - zpos - 1, sz_ - 1);
 
+  if (xmax == 0 || ymax == 0 || (zmax == 0 && nz_ > 1))
+    Tools::Error("Can't have a subdomain of size 1", __FILE__, __LINE__);
+
   int pvar = -1;
   for (int i = 0; i < dof_; i++)
     if (variableType_[i] == 3)
diff --git a/src/HYMLS_MainUtils.cpp b/src/HYMLS_MainUtils.cpp
index 475f1117..a2334ea2 100755
--- a/src/HYMLS_MainUtils.cpp
+++ b/src/HYMLS_MainUtils.cpp
@@ -225,9 +225,9 @@ Teuchos::RCP<Epetra_Vector> create_testvector(
       {
       hymls_gidx grid = matrix.GRID64(i);
       if (grid % dof == 0)
-        (*testvector)[i] = ((grid / dof) % 2) * 2 - 1;
+        (*testvector)[i] = (((grid / dof) % nx) % 2) * 2 - 1;
       else if (grid % dof == 1)
-        (*testvector)[i] = ((grid / dof / nx) % 2) * 2 - 1;
+        (*testvector)[i] = (((grid / dof / nx) % ny) % 2) * 2 - 1;
       else if (dim > 2 && grid % dof == 2 && eqn == "Stokes-B")
         (*testvector)[i] = ((grid / dof / nx / ny) % 2) * 2 - 1;
       else