diff --git a/releng/create_release.xsh b/releng/create_release.xsh
index 874f71a77..358124359 100644
--- a/releng/create_release.xsh
+++ b/releng/create_release.xsh
@@ -106,17 +106,17 @@ def upload_drv_paths_and_outputs(env: RelengEnvironment, paths: list[str]):
         raise subprocess.CalledProcessError(rv, proc.args)
 
 
-def make_manifest(eval_result):
-    manifest = {vs['system']: vs['outputs']['out'] for vs in eval_result}
+def make_manifest(builds_by_system):
+
     def manifest_line(system, out):
         return f'  {system} = "{out}";'
 
     manifest_text = textwrap.dedent("""\
         # This file was generated by releng/create_release.xsh in Lix
         {{
-          {lines}
+        {lines}
         }}
-    """).format(lines='\n'.join(manifest_line(s, p) for (s, p) in manifest.items()))
+    """).format(lines='\n'.join(manifest_line(s, p) for (s, p) in builds_by_system.items()))
 
     return manifest_text
 
@@ -142,6 +142,18 @@ def sha256_file(f: Path):
     return hasher.hexdigest()
 
 
+def extract_builds_by_system(eval_result):
+    # This could be a dictionary comprehension, but we want to be absolutely
+    # sure we don't have duplicates.
+    ret = {}
+    for attr in eval_result:
+        if attr['attrPath'][0] != 'build':
+            continue
+        assert attr['system'] not in ret
+        ret[attr['system']] = attr['outputs']['out']
+    return ret
+
+
 def make_artifacts_dir(eval_result, d: Path):
     d.mkdir(exist_ok=True, parents=True)
     version_dir = d / 'lix' / f'lix-{VERSION}'
@@ -150,12 +162,14 @@ def make_artifacts_dir(eval_result, d: Path):
     tarballs_drv = next(p for p in eval_result if p['attr'] == 'tarballs')
     cp --no-preserve=mode -r @(tarballs_drv['outputs']['out'])/* @(version_dir)
 
+    builds_by_system = extract_builds_by_system(eval_result)
+
     # FIXME: upgrade-nix searches for manifest.nix at root, which is rather annoying
     with open(d / 'manifest.nix', 'w') as h:
-        h.write(make_manifest(eval_result))
+        h.write(make_manifest(builds_by_system))
 
     with open(version_dir / 'manifest.nix', 'w') as h:
-        h.write(make_manifest(eval_result))
+        h.write(make_manifest(builds_by_system))
 
     print('[+] Make sources tarball')