diff --git a/libavcodec/av1dec.c b/libavcodec/av1dec.c
index 90621caeb6..a7383a88be 100644
--- a/libavcodec/av1dec.c
+++ b/libavcodec/av1dec.c
@@ -99,12 +99,11 @@ static int32_t decode_signed_subexp_with_ref(uint32_t sub_exp, int low,
 
 static void read_global_param(AV1DecContext *s, int type, int ref, int idx)
 {
-    uint8_t primary_frame, prev_frame;
+    int primary_frame;
     uint32_t abs_bits, prec_bits, round, prec_diff, sub, mx;
     int32_t r, prev_gm_param;
 
     primary_frame = s->raw_frame_header->primary_ref_frame;
-    prev_frame = s->raw_frame_header->ref_frame_idx[primary_frame];
     abs_bits = AV1_GM_ABS_ALPHA_BITS;
     prec_bits = AV1_GM_ALPHA_PREC_BITS;
 
@@ -114,8 +113,10 @@ static void read_global_param(AV1DecContext *s, int type, int ref, int idx)
      */
     if (s->raw_frame_header->primary_ref_frame == AV1_PRIMARY_REF_NONE)
         prev_gm_param = s->cur_frame.gm_params[ref][idx];
-    else
+    else {
+        int prev_frame = s->raw_frame_header->ref_frame_idx[primary_frame];
         prev_gm_param = s->ref[prev_frame].gm_params[ref][idx];
+    }
 
     if (idx < 2) {
         if (type == AV1_WARP_MODEL_TRANSLATION) {