diff --git a/selfdrive/modeld/transforms/transform.cc b/selfdrive/modeld/transforms/transform.cc
index 3ea799499f..056267aca8 100644
--- a/selfdrive/modeld/transforms/transform.cc
+++ b/selfdrive/modeld/transforms/transform.cc
@@ -28,7 +28,7 @@ void transform_queue(Transform* s,
                      cl_mem in_yuv, int in_width, int in_height,
                      cl_mem out_y, cl_mem out_u, cl_mem out_v,
                      int out_width, int out_height,
-                     mat3 projection) {
+                     const mat3& projection) {
   const int zero = 0;
 
   // sampled using pixel center origin
diff --git a/selfdrive/modeld/transforms/transform.h b/selfdrive/modeld/transforms/transform.h
index 21933f4d1f..3bce6f8a72 100644
--- a/selfdrive/modeld/transforms/transform.h
+++ b/selfdrive/modeld/transforms/transform.h
@@ -25,4 +25,4 @@ void transform_queue(Transform* s, cl_command_queue q,
                      cl_mem yuv, int in_width, int in_height,
                      cl_mem out_y, cl_mem out_u, cl_mem out_v,
                      int out_width, int out_height,
-                     mat3 projection);
+                     const mat3& projection);