diff --git a/src/c_interface/tensor_field.c b/src/c_interface/tensor_field.c
index 2f44fe8e6c8e7f30adf753a3b938528c1e98eb54..ccef3f75084d44f94f8e34da69b31ab14fb2473b 100644
--- a/src/c_interface/tensor_field.c
+++ b/src/c_interface/tensor_field.c
@@ -82,7 +82,7 @@ void tensor_field_deallocate(tensor_field field) {
 }
 
 void tensor_field_from_futhark_f32_4d_inplace(futhark_4d *f, struct futhark_context *ctx, tensor_field field) {
-#ifdef DEBUG
+#ifndef NDEBUG
     const int64_t *shape = futhark_shape_4d(ctx, f);
     fint nx = shape[0];
     fint ny = shape[1];