diff --git a/writeimg.c b/writeimg.c
index 6533771..4162006 100644
--- a/writeimg.c
+++ b/writeimg.c
@@ -24,7 +24,7 @@
 #endif
 
 #ifndef BLOCKSIZE
-#define BLOCKSIZE (4 * 1024 * 1024)
+#define BLOCKSIZE (1024 * 1024)
 #endif
 
 #define BYTES_TO_MIB(bts) ((double)bts / (1024 * 1024))