diff --git a/av1/encoder/tpl_model.c b/av1/encoder/tpl_model.c
index dd3d9c6..f1769b2 100644
--- a/av1/encoder/tpl_model.c
+++ b/av1/encoder/tpl_model.c
@@ -476,7 +476,7 @@
   // unavailable, the pointer will be set to Null.
   for (idx = 0; idx < INTER_REFS_PER_FRAME; ++idx) {
     int rf_idx = gf_group->ref_frame_gop_idx[frame_idx][idx];
-    if (rf_idx > 0) ref_frame[idx] = gf_picture[rf_idx];
+    if (rf_idx != -1) ref_frame[idx] = gf_picture[rf_idx];
   }
 
   xd->mi = cm->mi_grid_visible;