diff --git a/flake.nix b/flake.nix
index c918f65..082d9c2 100644
--- a/flake.nix
+++ b/flake.nix
@@ -385,7 +385,9 @@
             export PATH=${pkgs.qemu}/bin:$PATH
             IMGDIR=$(mktemp -d /tmp/not-os-qemu-XXXXXX)
             BASE=$(realpath $(dirname $0))
-            qemu-img create -F raw -f qcow2 -b $BASE/sd-image.img $IMGDIR/sd-overlay.qcow2 512M
+
+            qemu-img convert -O qcow2 -f raw -o preallocation=metadata $BASE/sd-image.img $IMGDIR/sd-sparse.qcow2
+            qemu-img create -F qcow2 -f qcow2 -b $IMGDIR/sd-sparse.qcow2 $IMGDIR/sd-overlay.qcow2 1G
 
             # Some command arguments are based from samples in Xilinx QEMU User Documentation
             # See: https://xilinx-wiki.atlassian.net/wiki/spaces/A/pages/821854273/Running+Bare+Metal+Applications+on+QEMU