diff --git a/libavformat/evc.c b/libavformat/evc.c
index 928ae1ff65..6a63630b0c 100644
--- a/libavformat/evc.c
+++ b/libavformat/evc.c
@@ -257,10 +257,10 @@ static int evcc_write(AVIOContext *pb, EVCDecoderConfigurationRecord *evcc)
     avio_wb16(pb, evcc->pic_height_in_luma_samples);
 
     /*
-     * bit(6) reserved = '111111'b;
-     * unsigned int(2) chromaFormat;
+     * unsigned int(6) reserved = '000000'b;
+     * unsigned int(2) lengthSizeMinusOne;
      */
-    avio_w8(pb, evcc->lengthSizeMinusOne | 0xfc);
+    avio_w8(pb, evcc->lengthSizeMinusOne & 0x3);
 
     /* unsigned int(8) numOfArrays; */
     avio_w8(pb, evcc->num_of_arrays);
diff --git a/tests/ref/lavf-fate/evc.mp4 b/tests/ref/lavf-fate/evc.mp4
index 4b410b84f3..6ef7af4ddc 100644
--- a/tests/ref/lavf-fate/evc.mp4
+++ b/tests/ref/lavf-fate/evc.mp4
@@ -1,3 +1,3 @@
-885fb330b20632b88ef9d7fb03dfa2e9 *tests/data/lavf-fate/lavf.evc.mp4
+bebb66fc3e13ece081d1aa96802e3c1f *tests/data/lavf-fate/lavf.evc.mp4
 37386 tests/data/lavf-fate/lavf.evc.mp4
 tests/data/lavf-fate/lavf.evc.mp4 CRC=0x48063f85