diff --git a/libs/pageserver_api/src/key.rs b/libs/pageserver_api/src/key.rs
index d680a5600e..3e1bba2a06 100644
--- a/libs/pageserver_api/src/key.rs
+++ b/libs/pageserver_api/src/key.rs
@@ -142,7 +142,7 @@ impl Key {
 }
 
 pub fn is_rel_block_key(key: &Key) -> bool {
-    key.field1 == 0x00 && key.field4 != 0
+    key.field1 == 0x00 && key.field4 != 0 && key.field6 != 0xffffffff
 }
 
 impl std::str::FromStr for Key {
diff --git a/libs/pageserver_api/src/shard.rs b/libs/pageserver_api/src/shard.rs
index a186d93bce..18ef2be523 100644
--- a/libs/pageserver_api/src/shard.rs
+++ b/libs/pageserver_api/src/shard.rs
@@ -530,12 +530,7 @@ fn key_is_shard0(key: &Key) -> bool {
     // relation pages are distributed to shards other than shard zero. Everything else gets
     // stored on shard 0.  This guarantees that shard 0 can independently serve basebackup
     // requests, and any request other than those for particular blocks in relations.
-    //
-    // In this condition:
-    // - is_rel_block_key includes only relations, i.e. excludes SLRU data and
-    // all metadata.
-    // - field6 is set to -1 for relation size pages.
-    !(is_rel_block_key(key) && key.field6 != 0xffffffff)
+    !is_rel_block_key(key)
 }
 
 /// Provide the same result as the function in postgres `hashfn.h` with the same name