diff --git a/libavformat/crypto.c b/libavformat/crypto.c
index 2999f50046..31a438c94c 100644
--- a/libavformat/crypto.c
+++ b/libavformat/crypto.c
@@ -26,7 +26,8 @@
 #include "internal.h"
 #include "url.h"
 
-#define MAX_BUFFER_BLOCKS 150
+// encourage reads of 4096 bytes - 1 block is always retained.
+#define MAX_BUFFER_BLOCKS 257
 #define BLOCKSIZE 16
 
 typedef struct CryptoContext {