diff --git a/pytorch3d/csrc/knn/knn.cu b/pytorch3d/csrc/knn/knn.cu
index c679362e..c4c87d7c 100644
--- a/pytorch3d/csrc/knn/knn.cu
+++ b/pytorch3d/csrc/knn/knn.cu
@@ -505,7 +505,7 @@ std::tuple<at::Tensor, at::Tensor> KNearestNeighborBackwardCuda(
   const auto D = p2.size(2);
   const auto K = idxs.size(2);
 
-  TORCH_CHECK(p2.size(2) == D, "Point sets must have the same last dimension");
+  TORCH_CHECK(p1.size(2) == D, "Point sets must have the same last dimension");
   TORCH_CHECK(idxs.size(0) == N, "KNN idxs must have the same batch dimension");
   TORCH_CHECK(
       idxs.size(1) == P1, "KNN idxs must have the same point dimension as p1");