diff --git a/board/raspberrypi/post-image.sh b/board/raspberrypi/post-image.sh
index 70447cd48b..bf9af5dc60 100755
--- a/board/raspberrypi/post-image.sh
+++ b/board/raspberrypi/post-image.sh
@@ -49,10 +49,18 @@ __EOF__
 
 done
 
+# Pass an empty rootpath. genimage makes a full copy of the given rootpath to
+# ${GENIMAGE_TMP}/root so passing TARGET_DIR would be a waste of time and disk
+# space. We don't rely on genimage to build the rootfs image, just to insert a
+# pre-built one in the disk image.
+
+trap 'rm -rf "${ROOTPATH_TMP}"' EXIT
+ROOTPATH_TMP="$(mktemp -d)"
+
 rm -rf "${GENIMAGE_TMP}"
 
-genimage                           \
-	--rootpath "${TARGET_DIR}"     \
+genimage \
+	--rootpath "${ROOTPATH_TMP}"   \
 	--tmppath "${GENIMAGE_TMP}"    \
 	--inputpath "${BINARIES_DIR}"  \
 	--outputpath "${BINARIES_DIR}" \