diff --git a/commands/nand-bitflip.c b/commands/nand-bitflip.c
index fe56f22..a8a97c1 100644
--- a/commands/nand-bitflip.c
+++ b/commands/nand-bitflip.c
@@ -69,6 +69,10 @@
 
 	block += mtd_div_by_eb(offset, meminfo.mtd);
 	offset = mtd_mod_by_eb(offset, meminfo.mtd);
+	if ((int)offset % meminfo.mtd->writesize) {
+		printf("offset has to be pagesize aligned\n");
+		return 1;
+	}
 
 	if (!check) {
 		ret = mtd_peb_create_bitflips(meminfo.mtd, block, offset, meminfo.writesize,
diff --git a/drivers/mtd/peb.c b/drivers/mtd/peb.c
index 66227d4..c35b63f 100644
--- a/drivers/mtd/peb.c
+++ b/drivers/mtd/peb.c
@@ -565,6 +565,8 @@
 
 	if (offset < 0 || offset + len > mtd->erasesize)
 		return -EINVAL;
+	if (offset % mtd->writesize)
+		return -EINVAL;
 	if (len <= 0)
 		return -EINVAL;
 	if (num_bitflips <= 0)
@@ -610,7 +612,7 @@
 	for (i = 0; i < num_bitflips; i++) {
 		int offs;
 		int bit;
-		u8 *pos = buf;
+		u8 *pos = buf + offset;
 
 		if (random) {
 			offs = random32() % len;