diff --git a/sys/dev/disk/amd/amd.c b/sys/dev/disk/amd/amd.c
--- a/sys/dev/disk/amd/amd.c
+++ b/sys/dev/disk/amd/amd.c
@@ -396,8 +396,8 @@
 		pSRB->pccb = pccb;
 		pccb->ccb_h.ccb_srb_ptr = pSRB;
 		pccb->ccb_h.ccb_amd_ptr = amd;
-		pSRB->ScsiCmdLen = pcsio->cdb_len;
-		bcopy(pcsio->cdb_io.cdb_bytes, pSRB->CmdBlock, pcsio->cdb_len);
+		pSRB->ScsiCmdLen = imin(pcsio->cdb_len, (int)sizeof(pSRB->CmdBlock));
+		bcopy(pcsio->cdb_io.cdb_bytes, pSRB->CmdBlock, pSRB->ScsiCmdLen);
 		if ((pccb->ccb_h.flags & CAM_DIR_MASK) != CAM_DIR_NONE) {
 			if ((pccb->ccb_h.flags & CAM_SCATTER_VALID) == 0) {
 				/*