diff --git a/libavcodec/ra144.c b/libavcodec/ra144.c
index e09d38f231..7ff1b13bce 100644
--- a/libavcodec/ra144.c
+++ b/libavcodec/ra144.c
@@ -289,13 +289,11 @@ static int dec2(RA144Context *ractx, int16_t *decsp, int block_num,
                 int copynew, int f)
 {
     int work[10];
-    int a = block_num + 1;
-    int b = NBLOCKS - a;
 
     // Interpolate block coefficients from the this frame forth block and
     // last frame forth block
     ff_acelp_weighted_vector_sum(decsp, ractx->lpc_coef, ractx->lpc_coef_old,
-                                 a, b, 0, 2, 30);
+                                 block_num + 1, 3 - block_num, 0, 2, 30);
 
     if (eq(decsp, work)) {
         // The interpolated coefficients are unstable, copy either new or old