diff --git a/CHANGELOG b/CHANGELOG
index 24efe49550..624d23dfd6 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,11 @@
+git-annex (10.20250321) UNRELEASED; urgency=medium
+
+  * updatecluster, updateproxy: When a remote that has no annex-uuid is
+    configured as annex-cluster-node, warn and avoid writing bad data to
+    the git-annex branch.
+
+ -- Joey Hess <id@joeyh.name>  Fri, 21 Mar 2025 12:27:11 -0400
+
 git-annex (10.20250320) upstream; urgency=medium
 
   * Added the compute special remote.
diff --git a/Command/UpdateCluster.hs b/Command/UpdateCluster.hs
index 003ab48ed6..be271d64fc 100644
--- a/Command/UpdateCluster.hs
+++ b/Command/UpdateCluster.hs
@@ -38,7 +38,7 @@ start = startingCustomOutput (ActionItemOther Nothing) $ do
 		Nothing -> return Nothing
 		Just [] -> return Nothing
 		Just clusternames -> 
-			ifM (Command.UpdateProxy.checkCanProxy r "Cannot use this special remote as a cluster node.")
+			ifM (Command.UpdateProxy.checkCanProxy r "Cannot use this remote as a cluster node.")
 				( return $ Just $ M.fromList $
 					zip clusternames (repeat (S.singleton r))
 				, return Nothing
diff --git a/Command/UpdateProxy.hs b/Command/UpdateProxy.hs
index 88a8ecaf77..006e618b60 100644
--- a/Command/UpdateProxy.hs
+++ b/Command/UpdateProxy.hs
@@ -59,24 +59,32 @@ start = startingCustomOutput (ActionItemOther Nothing) $ do
 	
 	isproxy r
 		| remoteAnnexProxy (R.gitconfig r) || not (null (remoteAnnexClusterNode (R.gitconfig r))) = 
-			checkCanProxy r "Cannot proxy to this special remote."
+			checkCanProxy r "Cannot proxy to this remote."
 		| otherwise = pure False
 
 checkCanProxy :: Remote -> String -> Annex Bool
-checkCanProxy r cannotmessage = 
-	ifM (R.isExportSupported r)
-		( if annexObjects (R.config r)
-			then pure True
-			else do
-				warnannexobjects
-				pure False
-		, pure True
-		)
+checkCanProxy r cannotmessage
+	| R.uuid r == NoUUID = do
+		warning $ UnquotedString $ unwords
+			[ R.name r
+			, "is a git remote without a known annex-uuid."
+			, cannotmessage
+			]
+		pure False
+	| otherwise =
+		ifM (R.isExportSupported r)
+			( if annexObjects (R.config r)
+				then pure True
+				else do
+					warnannexobjects
+					pure False
+			, pure True
+			)
   where
 	warnannexobjects = warning $ UnquotedString $ unwords
 		[ R.name r
-		, "is configured with exporttree=yes, but without"
-		, "annexobjects=yes."
+		, "is a special remote configured with exporttree=yes,"
+		, "but without annexobjects=yes."
 		, cannotmessage
 		, "Suggest you run: git-annex enableremote"
 		, R.name r