diff --git a/metadata/layout.conf b/metadata/layout.conf
index 31a7f05..a5a78da 100644
--- a/metadata/layout.conf
+++ b/metadata/layout.conf
@@ -12,6 +12,11 @@ masters = gentoo
 # Control the signing.
 sign-commits = true
 thin-manifests = true
+# 2021-05-15: Do not sign manifests anymore.
+#  - It's breaks pkgcheck (see https://github.com/pkgcore/pkgcheck/issues/307).
+#  - AFAIK it's not supported by portage.
+#  - The commits themselves are signed.
+sign-manifests = false
 
 # Copied from the main tree.
 # manifest-hashes specify hashes used for new/updated entries