diff --git a/hook-functions b/hook-functions
index f673292..3c9a243 100644
--- a/hook-functions
+++ b/hook-functions
@@ -158,7 +158,8 @@ add_builtin_firmware()
 # * If the target is not specified, it defaults to the source file
 #   name.
 # * If the target is specified and exists as a directory under
-#   $DESTDIR, the basename of the source is appended to it.
+#   $DESTDIR or ends in a slash, the basename of the source is
+#   appended to it.
 #
 # The target file's containing directories are created if necessary.
 #
@@ -180,7 +181,7 @@ copy_file() {
 
 	[ -f "${src}" ] || return 2
 
-	if [ -d "${DESTDIR}/${target}" ]; then
+	if [ -d "${DESTDIR}/${target}" ] || [ "${target%/}" != "$target" ]; then
 		target="${target}/${src##*/}"
 	fi