diff --git a/libavcodec/mpegvideo_enc.c b/libavcodec/mpegvideo_enc.c
index 9f8682cae5..8fbd7595c1 100644
--- a/libavcodec/mpegvideo_enc.c
+++ b/libavcodec/mpegvideo_enc.c
@@ -351,7 +351,7 @@ av_cold int MPV_encode_init(AVCodecContext *avctx)
         av_log(avctx, AV_LOG_INFO, "impossible bitrate constraints, this will fail\n");
     }
 
-    if(avctx->rc_buffer_size && avctx->bit_rate*av_q2d(avctx->time_base) > avctx->rc_buffer_size){
+    if(avctx->rc_buffer_size && avctx->bit_rate*(int64_t)avctx->time_base.num > avctx->rc_buffer_size * (int64_t)avctx->time_base.den){
         av_log(avctx, AV_LOG_ERROR, "VBV buffer too small for bitrate\n");
         return -1;
     }