diff --git a/libavcodec/libx264.c b/libavcodec/libx264.c
index 06e917e4f3..4f44a06548 100644
--- a/libavcodec/libx264.c
+++ b/libavcodec/libx264.c
@@ -179,7 +179,8 @@ static int X264_frame(AVCodecContext *ctx, AVPacket *pkt, const AVFrame *frame,
             x264_encoder_reconfig(x4->enc, &x4->params);
         }
 
-        if (x4->params.rc.i_rc_method == X264_RC_CRF &&
+        if (x4->crf >= 0 &&
+            x4->params.rc.i_rc_method == X264_RC_CRF &&
             x4->params.rc.f_rf_constant != x4->crf) {
             x4->params.rc.f_rf_constant = x4->crf;
             x264_encoder_reconfig(x4->enc, &x4->params);
@@ -191,7 +192,7 @@ static int X264_frame(AVCodecContext *ctx, AVPacket *pkt, const AVFrame *frame,
             x264_encoder_reconfig(x4->enc, &x4->params);
         }
 
-        if (x4->crf_max &&
+        if (x4->crf_max >= 0 &&
             x4->params.rc.f_rf_constant_max != x4->crf_max) {
             x4->params.rc.f_rf_constant_max = x4->crf_max;
             x264_encoder_reconfig(x4->enc, &x4->params);