diff --git a/tools/mkversion.sh b/tools/mkversion.sh
index a83c94e71..9a147c061 100755
--- a/tools/mkversion.sh
+++ b/tools/mkversion.sh
@@ -65,6 +65,9 @@ sha=$(
     [ -f armsrc/appmain.c ] || return
     ls armsrc/*.[ch] common_arm/*.[ch]|grep -E -v "(disabled|version_pm3|fpga_version_info)"|xargs sha256sum|sha256sum|cut -c -9
 )
+if [ "$sha" = "" ]; then
+  sha="no sha256"
+fi
 cat <<EOF
 #include "common.h"
 /* Generated file, do not edit */