diff --git a/libavcodec/vaapi_encode.c b/libavcodec/vaapi_encode.c
index 070ff5f244..7e9c00f51d 100644
--- a/libavcodec/vaapi_encode.c
+++ b/libavcodec/vaapi_encode.c
@@ -1433,7 +1433,7 @@ av_cold int ff_vaapi_encode_init(AVCodecContext *avctx)
     ctx->output_order = - ctx->output_delay - 1;
 
     // Currently we never generate I frames, only IDR.
-    ctx->p_per_i = ((avctx->gop_size + avctx->max_b_frames) /
+    ctx->p_per_i = ((avctx->gop_size - 1 + avctx->max_b_frames) /
                     (avctx->max_b_frames + 1));
     ctx->b_per_p = avctx->max_b_frames;