diff --git a/libavformat/movenc.c b/libavformat/movenc.c
index 40465e80fc..206c4be3dd 100644
--- a/libavformat/movenc.c
+++ b/libavformat/movenc.c
@@ -3209,7 +3209,7 @@ int ff_mov_write_packet(AVFormatContext *s, AVPacket *pkt)
     }
 
     if (trk->entry >= trk->cluster_capacity) {
-        unsigned new_capacity = trk->entry + MOV_INDEX_CLUSTER_SIZE;
+        unsigned new_capacity = 2*(trk->entry + MOV_INDEX_CLUSTER_SIZE);
         if (av_reallocp_array(&trk->cluster, new_capacity,
                               sizeof(*trk->cluster)))
             return AVERROR(ENOMEM);
diff --git a/libavformat/movenc.h b/libavformat/movenc.h
index 6b583d5577..456ed0c4f7 100644
--- a/libavformat/movenc.h
+++ b/libavformat/movenc.h
@@ -26,7 +26,7 @@
 
 #include "avformat.h"
 
-#define MOV_INDEX_CLUSTER_SIZE 16384
+#define MOV_INDEX_CLUSTER_SIZE 1024
 #define MOV_TIMESCALE 1000
 
 #define RTP_MAX_PACKET_SIZE 1450