diff --git a/libguestfs.spec b/libguestfs.spec
index c5c0e5d..8b93ea3 100644
--- a/libguestfs.spec
+++ b/libguestfs.spec
@@ -382,7 +382,8 @@ test -n "$ext_cmds"
 # guestfs may call mkfs, but it cant tell in advance which filesystems
 # it must support. Collect a manual list of possible filesystems so that
 # the commands get included in the initrd.
-for fs in \
+ext_cmds="$ext_cmds
+` for fs in \
 	ext2 \
 	ext3 \
 	ext4 \
@@ -397,7 +398,8 @@ for fs in \
 ; do
 	echo mkfs.$fs
 	echo fsck.$fs
-done >> ext_cmds.txt
+done
+`  "
 #
 for cmd in ls $ext_cmds
 do