diff --git a/bootloader/build_multi_image.sh b/bootloader/build_multi_image.sh
index 94a3b46b12b2ead338da2d14794ff19cc4c08278..15212e4350d7f16d1277b25b287eeb35182c9f26 100755
--- a/bootloader/build_multi_image.sh
+++ b/bootloader/build_multi_image.sh
@@ -6,8 +6,8 @@ BIN1="$2"
 BIN2="$3"
 BINOUT="$4"
 
-dd if=/dev/zero ibs=1k count=448 2>/dev/null | tr "\000" "\377" > "$BINOUT"
+dd if=/dev/zero ibs=1k count=448 2>/dev/null | LANG=C tr "\000" "\377" > "$BINOUT"
 dd if="$BIN1" of="$BINOUT" conv=notrunc 2>/dev/null
-dd if="$BIN2" of="$BINOUT" conv=notrunc oflag=append 2>/dev/null
+dd if="$BIN2" >> "$BINOUT" 2>/dev/null
 
 "$PYTHON" "$(dirname "$0")/crc_patch.py" "$BINOUT"