diff --git a/libavcodec/xbmenc.c b/libavcodec/xbmenc.c
index b25615f2a4..3fc0e3185a 100644
--- a/libavcodec/xbmenc.c
+++ b/libavcodec/xbmenc.c
@@ -27,11 +27,12 @@
 static int xbm_encode_frame(AVCodecContext *avctx, AVPacket *pkt,
                             const AVFrame *p, int *got_packet)
 {
-    int i, j, ret, size, linesize;
+    int i, j, commas, ret, size, linesize;
     uint8_t *ptr, *buf;
 
     linesize = (avctx->width + 7) / 8;
-    size     = avctx->height * (linesize * 7 + 2) + 110;
+    commas   = avctx->height * linesize;
+    size     = avctx->height * (linesize * 7 + 2) + 109;
     if ((ret = ff_alloc_packet2(avctx, pkt, size, 0)) < 0)
         return ret;
 
@@ -42,8 +43,11 @@ static int xbm_encode_frame(AVCodecContext *avctx, AVPacket *pkt,
     buf += snprintf(buf, 33, "#define image_height %u\n", avctx->height);
     buf += snprintf(buf, 40, "static unsigned char image_bits[] = {\n");
     for (i = 0; i < avctx->height; i++) {
-        for (j = 0; j < linesize; j++)
-            buf += snprintf(buf, 7, " 0x%02X,", ff_reverse[*ptr++]);
+        for (j = 0; j < linesize; j++) {
+            buf += snprintf(buf, 6, " 0x%02X", ff_reverse[*ptr++]);
+            if (--commas > 0)
+                buf += snprintf(buf, 2, ",");
+        }
         ptr += p->linesize[0] - linesize;
         buf += snprintf(buf, 2, "\n");
     }
diff --git a/tests/ref/lavf/xbm b/tests/ref/lavf/xbm
index bc157834ff..e54d6bc226 100644
--- a/tests/ref/lavf/xbm
+++ b/tests/ref/lavf/xbm
@@ -1,3 +1,3 @@
-0629055fd82366317c651a0af4bb82d7 *tests/data/images/xbm/02.xbm
+83ed197cc88f382d9253365ffef70ec5 *tests/data/images/xbm/02.xbm
 tests/data/images/xbm/%02d.xbm CRC=0xc9a20204
-76411 tests/data/images/xbm/02.xbm
+76410 tests/data/images/xbm/02.xbm