1 files changed, 2 insertions, 1 deletions
diff --git a/halfkay.c b/halfkay.c
index 899e456..755a84e 100644
--- a/halfkay.c
+++ b/halfkay.c
@@ -89,10 +89,11 @@ static void usbsendcmd(void *data, size_t size, bool firstxfer)
 
 static void fmtcmd(void *_dest, const struct flashparams *fp, size_t addr)
 {
+	static const size_t MAX_SHIFT = sizeof addr * CHAR_BIT / 8;
 	unsigned char *dest = _dest;
 
 	addr >>= fp->addrshft;
-	for (size_t i = 0; i < fp->cmdsz; i++)
+	for (size_t i = 0; i < fp->cmdsz && i < MAX_SHIFT; i++)
 		dest[i] = (addr >> (i * 8)) & 0xFF;
 }