diff --git a/build.sh b/build.sh
index e6d5446..ef795b4 100755
--- a/build.sh
+++ b/build.sh
@@ -130,6 +130,9 @@ fi
 cp -v "${OUTPUT}_live.efi" "${OUTPUT}/efi-template/EFI/Linux/$EFI"
 systemd-repart --no-pager --empty=allow --size=auto --dry-run=no --root="${OUTPUT}" --definitions=mkosi.repart --defer-partitions=root "$IMG"
 
+# Finally rebuild the actual image file with appropriate partition sizing. In particular with squeezed btrfs.
+./part-rebuild.py "$IMG"
+
 # TODO before accepting new uploads perform sanity checks on the artifacts (e.g. the tar being well formed)
 chmod go+r ./*.efi # efi images are 700, make them readable so the server can serve them
 ls -lah
diff --git a/mkosi.repart-rebuild/00-esp.conf b/mkosi.repart-rebuild/00-esp.conf
new file mode 100644
index 0000000..0015dd0
--- /dev/null
+++ b/mkosi.repart-rebuild/00-esp.conf
@@ -0,0 +1,7 @@
+# SPDX-License-Identifier: GPL-2.0-only OR GPL-3.0-only OR LicenseRef-KDE-Accepted-GPL
+# SPDX-FileCopyrightText: 2023 Harald Sitter <sitter@kde.org>
+
+[Partition]
+Type=esp
+SplitName=esp
+CopyBlocks=/esp.raw
diff --git a/mkosi.repart-rebuild/50-root.conf b/mkosi.repart-rebuild/50-root.conf
new file mode 100644
index 0000000..ac439c8
--- /dev/null
+++ b/mkosi.repart-rebuild/50-root.conf
@@ -0,0 +1,8 @@
+# SPDX-License-Identifier: GPL-2.0-only OR GPL-3.0-only OR LicenseRef-KDE-Accepted-GPL
+# SPDX-FileCopyrightText: 2023 Harald Sitter <sitter@kde.org>
+
+[Partition]
+Type=root
+Label=KDEOSLive
+SplitName=root
+CopyBlocks=/KDEOSLive.raw
diff --git a/mkosi.repart-rebuild/README.md b/mkosi.repart-rebuild/README.md
new file mode 100644
index 0000000..c3995d7
--- /dev/null
+++ b/mkosi.repart-rebuild/README.md
@@ -0,0 +1,9 @@
+<!--
+SPDX-License-Identifier: CC0-1.0
+SPDX-FileCopyrightText: 2024 Harald Sitter <sitter@kde.org>
+-->
+
+This isn't actually used by mkosi but named like it so it is next to the actual mkosi directory.
+The configs in here simply pick up split partitions from the original repart run into a rebuild run.
+
+Also see part-rebuild.py
diff --git a/mkosi.repart/50-root.conf b/mkosi.repart/50-root.conf
index 7a50cae..d91fb4c 100644
--- a/mkosi.repart/50-root.conf
+++ b/mkosi.repart/50-root.conf
@@ -5,6 +5,7 @@
 Type=root
 Format=btrfs
 SizeMinBytes=1G
+# Do not use spaces. We need to extract this later as a file path.
 Label=KDEOSLive
 SplitName=root
 # NOTE: the FS isn't read only because we have mutable subvolumes. Individual subvolumes may be readonly though.
diff --git a/part-rebuild.py b/part-rebuild.py
new file mode 100755
index 0000000..153328d
--- /dev/null
+++ b/part-rebuild.py
@@ -0,0 +1,40 @@
+#!/usr/bin/env python3
+
+# SPDX-License-Identifier: GPL-2.0-only OR GPL-3.0-only OR LicenseRef-KDE-Accepted-GPL
+# SPDX-FileCopyrightText: 2024 Harald Sitter <sitter@kde.org>
+
+# Rebuilds the image using appropriate partition sizes.
+
+import json
+import math
+import subprocess
+from subprocess import check_output
+import sys
+import os
+
+RAW = sys.argv[1]
+
+# Load the partition table
+out = check_output(["sfdisk", "--json", RAW])
+data = json.loads(out)
+partitiontable = data["partitiontable"]
+sectorsize = partitiontable["sectorsize"]
+partitions = partitiontable["partitions"]
+
+# Find the root partition
+root_partition = None
+for index, partition in enumerate(partitions):
+    if partition["name"] == "KDEOSLive":
+        root_partition = partition
+
+# Update its size to what it actually is on the filesystem level
+btrfs = json.loads(open("btrfs.json").read())
+root_partition["size"] = math.ceil(btrfs['size'] / sectorsize)
+
+# Fish out the partitions with appropriate skip and count values (i.e. the actual filesystem sizes)
+for index, partition in enumerate(partitions):
+    subprocess.run(["dd", f"if={RAW}", f"of={partition["name"]}.raw", f"bs={sectorsize}", f"skip={partition["start"]}", f"count={partition["size"]}"], check=True)
+
+# Then reassemble them into a new image using those squeezed partition images.
+open(RAW, "w").close()
+subprocess.run(["systemd-repart", "--empty=allow", "--dry-run=no", "--definitions=mkosi.repart-rebuild", "--root", os.getcwd(), RAW], check=True)