diff --git a/pageserver/src/tenant/mgr.rs b/pageserver/src/tenant/mgr.rs
index 0a494e7923..248d92622e 100644
--- a/pageserver/src/tenant/mgr.rs
+++ b/pageserver/src/tenant/mgr.rs
@@ -2200,7 +2200,7 @@ impl TenantManager {
         selector: ShardSelector,
     ) -> ShardResolveResult {
         let tenants = self.tenants.read().unwrap();
-        let mut want_shard = None;
+        let mut want_shard: Option<ShardIndex> = None;
         let mut any_in_progress = None;
 
         match &*tenants {
@@ -2225,14 +2225,23 @@ impl TenantManager {
                             return ShardResolveResult::Found(tenant.clone());
                         }
                         ShardSelector::Page(key) => {
-                            // First slot we see for this tenant, calculate the expected shard number
-                            // for the key: we will use this for checking if this and subsequent
-                            // slots contain the key, rather than recalculating the hash each time.
-                            if want_shard.is_none() {
-                                want_shard = Some(tenant.shard_identity.get_shard_number(&key));
+                            // Each time we find an attached slot with a different shard count,
+                            // recompute the expected shard number: during shard splits we might
+                            // have multiple shards with the old shard count.
+                            if want_shard.is_none()
+                                || want_shard.unwrap().shard_count != tenant.shard_identity.count
+                            {
+                                want_shard = Some(ShardIndex {
+                                    shard_number: tenant.shard_identity.get_shard_number(&key),
+                                    shard_count: tenant.shard_identity.count,
+                                });
                             }
 
-                            if Some(tenant.shard_identity.number) == want_shard {
+                            if Some(ShardIndex {
+                                shard_number: tenant.shard_identity.number,
+                                shard_count: tenant.shard_identity.count,
+                            }) == want_shard
+                            {
                                 return ShardResolveResult::Found(tenant.clone());
                             }
                         }