diff --git a/mkninja.sh b/mkninja.sh
index f80e2f1c..c49286db 100644
--- a/mkninja.sh
+++ b/mkninja.sh
@@ -516,6 +516,8 @@ FORMATS="\
     ibm360_525 \
     ibm720 \
     ibm720_525 \
+    bk800 \
+    bk800_525 \
     mac400 \
     mac800 \
     micropolis143 \
diff --git a/src/formats/bk800.textpb b/src/formats/bk800.textpb
index c69427f0..f7eeb98e 100644
--- a/src/formats/bk800.textpb
+++ b/src/formats/bk800.textpb
@@ -23,7 +23,7 @@ image_writer {
 encoder {
 	ibm {
 		trackdata {
-			track_length_ms: 200
+			track_length_ms: 280
 			clock_rate_khz: 250
 			sectors {
 				sector: 1