diff --git a/R/kdtree.R b/R/kdtree.R
index 5d202b8..5f990a2 100644
--- a/R/kdtree.R
+++ b/R/kdtree.R
@@ -160,7 +160,7 @@ interp_tris <- function(query_coordinates, mesh_vertices, nearest_face_vertices,
 interp_tris_cpp_wrapper <- function(query_coordinates, mesh_vertices, nearest_face_vertices, pervertex_data, iwd_beta = 2.0) {
 
   # adjust indexing for C++
-  nearest_face_vertices = nearest_face_vertices + 1L;
+  #nearest_face_vertices = nearest_face_vertices + 1L;
 
   return(.Call("interp_tris_c", query_coordinates, mesh_vertices, nearest_face_vertices, pervertex_data, iwd_beta));
 }
diff --git a/tests/testthat/test_kdtree.R b/tests/testthat/test_kdtree.R
index a0de9ed..31ca690 100644
--- a/tests/testthat/test_kdtree.R
+++ b/tests/testthat/test_kdtree.R
@@ -98,6 +98,14 @@ testthat::test_that("The R and CPP versions of the linear_interpolate_kdtree fun
   testthat::expect_true(is.double(dest_pervertex_data_CPP));
   testthat::expect_equal(length(dest_pervertex_data_CPP), nrow(dest_mesh$vertices));
 
+  # The min values should be zero for both.
+  testthat::expect_equal(min(dest_pervertex_data_R), 0.0);
+  testthat::expect_equal(min(dest_pervertex_data_CPP), 0.0);
+
+  # The max values are not identical for some reason (precision?), but should be in same range.
+  testthat::expect_true(max(dest_pervertex_data_R) > 4.6 & max(dest_pervertex_data_R) < 4.8);
+  testthat::expect_true(max(dest_pervertex_data_CPP) > 4.6 & max(dest_pervertex_data_CPP) < 4.8);
+
   # The real test for similar values:
   testthat::expect_equal(dest_pervertex_data_R, dest_pervertex_data_CPP, tolerance=1e-1);