diff --git a/changes/17819.md b/changes/17819.md
new file mode 100644
index 000000000000..344c12377317
--- /dev/null
+++ b/changes/17819.md
@@ -0,0 +1,2 @@
+Fix crash in ledger sync check that could occur when trying to load ledger
+databases that were only partially synced to a network ledger
diff --git a/src/lib/merkle_ledger/any_ledger.ml b/src/lib/merkle_ledger/any_ledger.ml
index dcc8845f20ee..f01943fa6739 100644
--- a/src/lib/merkle_ledger/any_ledger.ml
+++ b/src/lib/merkle_ledger/any_ledger.ml
@@ -81,6 +81,8 @@ module Make_base (Inputs : Intf.Inputs.Intf) :
 
     let set_at_index_exn (T ((module Base), t)) = Base.set_at_index_exn t
 
+    let get_at_index (T ((module Base), t)) = Base.get_at_index t
+
     let get_at_index_exn (T ((module Base), t)) = Base.get_at_index_exn t
 
     let set_batch ?hash_cache (T ((module Base), t)) =
@@ -118,6 +120,8 @@ module Make_base (Inputs : Intf.Inputs.Intf) :
 
     let token_owners (T ((module Base), t)) = Base.token_owners t
 
+    let iteri_untrusted (T ((module Base), t)) = Base.iteri_untrusted t
+
     let iteri (T ((module Base), t)) = Base.iteri t
 
     (* ignored_keys must be Base.Keys.Set.t, but that isn't necessarily the same as Keys.Set.t for the
diff --git a/src/lib/merkle_ledger/converting_merkle_tree.ml b/src/lib/merkle_ledger/converting_merkle_tree.ml
index 35f5c9ad386d..58dc18859a96 100644
--- a/src/lib/merkle_ledger/converting_merkle_tree.ml
+++ b/src/lib/merkle_ledger/converting_merkle_tree.ml
@@ -109,6 +109,8 @@ end)
 
   let to_list_sequential t = Primary_ledger.to_list_sequential t.primary_ledger
 
+  let iteri_untrusted t ~f = Primary_ledger.iteri_untrusted t.primary_ledger ~f
+
   let iteri t ~f = Primary_ledger.iteri t.primary_ledger ~f
 
   let foldi t ~init ~f = Primary_ledger.foldi t.primary_ledger ~init ~f
@@ -180,6 +182,8 @@ end)
          ~f:(fun (loc, account) -> (loc, convert account))
          located_accounts )
 
+  let get_at_index t idx = Primary_ledger.get_at_index t.primary_ledger idx
+
   let get_at_index_exn t idx =
     Primary_ledger.get_at_index_exn t.primary_ledger idx
 
@@ -264,12 +268,12 @@ struct
     Primary_db.num_accounts db1 = Converting_db.num_accounts db2
     &&
     let is_synced = ref true in
-    Primary_db.iteri db1 ~f:(fun idx stable_account ->
-        let expected_unstable_account = convert stable_account in
-        let actual_unstable_account = Converting_db.get_at_index_exn db2 idx in
+    Primary_db.iteri_untrusted db1 ~f:(fun idx stable_account ->
+        let expected_unstable_account = Option.map ~f:convert stable_account in
+        let actual_unstable_account = Converting_db.get_at_index db2 idx in
         if
           not
-            (Inputs.converted_equal expected_unstable_account
+            (Option.equal Inputs.converted_equal expected_unstable_account
                actual_unstable_account )
         then is_synced := false ) ;
     !is_synced
diff --git a/src/lib/merkle_ledger/database.ml b/src/lib/merkle_ledger/database.ml
index 2d2a138cea45..663dd4b010b7 100644
--- a/src/lib/merkle_ledger/database.ml
+++ b/src/lib/merkle_ledger/database.ml
@@ -278,9 +278,13 @@ module Make (Inputs : Intf.Inputs.DATABASE) = struct
       Option.map (last_location mdb) ~f:Location.to_path_exn
   end
 
-  let get_at_index_exn mdb index =
+  let get_at_index mdb index =
     let addr = Addr.of_int_exn ~ledger_depth:mdb.depth index in
-    get mdb (Location.Account addr) |> Option.value_exn
+    get mdb (Location.Account addr)
+
+  let get_at_index_exn mdb index =
+    get_at_index mdb index
+    |> Option.value_exn ~message:"Expected account at index" ~here:[%here]
 
   let all_accounts (t : t) =
     match Account_location.last_location_address t with
@@ -572,13 +576,19 @@ module Make (Inputs : Intf.Inputs.DATABASE) = struct
     | Ok location ->
         Ok (`Existed, location)
 
-  let iteri t ~f =
+  let iteri_untrusted t ~f =
     match Account_location.last_location_address t with
     | None ->
         ()
     | Some last_addr ->
         Sequence.range ~stop:`inclusive 0 (Addr.to_int last_addr)
-        |> Sequence.iter ~f:(fun i -> f i (get_at_index_exn t i))
+        |> Sequence.iter ~f:(fun i -> f i (get_at_index t i))
+
+  let iteri t ~f =
+    iteri_untrusted t ~f:(fun index account_opt ->
+        f index
+          (Option.value_exn ~message:"Expected account at index" ~here:[%here]
+             account_opt ) )
 
   (* TODO : if key-value store supports iteration mechanism, like RocksDB,
      maybe use that here, instead of loading all accounts into memory See Issue
diff --git a/src/lib/merkle_ledger/intf.ml b/src/lib/merkle_ledger/intf.ml
index 8be1280f5497..2e54882ad6c6 100644
--- a/src/lib/merkle_ledger/intf.ml
+++ b/src/lib/merkle_ledger/intf.ml
@@ -320,6 +320,9 @@ module Ledger = struct
     (** list of accounts via slower sequential mechanism *)
     val to_list_sequential : t -> account list
 
+    (** iterate over all indexes and accounts, if the ledger is not known to be sound *)
+    val iteri_untrusted : t -> f:(index -> account option -> unit) -> unit
+
     (** iterate over all indexes and accounts *)
     val iteri : t -> f:(index -> account -> unit) -> unit
 
@@ -391,6 +394,8 @@ module Ledger = struct
     val set_batch :
       ?hash_cache:hash Addr.Map.t -> t -> (Location.t * account) list -> unit
 
+    val get_at_index : t -> int -> account option
+
     val get_at_index_exn : t -> int -> account
 
     val set_at_index_exn : t -> int -> account -> unit
@@ -548,6 +553,8 @@ module Ledger = struct
 
       module Config : Config
 
+      val dbs_synced : primary_ledger -> converting_ledger -> bool
+
       (** Create a new converting merkle tree with the given configuration. If
       [In_directories] is given, existing databases will be opened and used to
       back the converting merkle tree. If the converting database does not exist
diff --git a/src/lib/merkle_ledger/null_ledger.ml b/src/lib/merkle_ledger/null_ledger.ml
index 066b62644fc6..2d22279fe23e 100644
--- a/src/lib/merkle_ledger/null_ledger.ml
+++ b/src/lib/merkle_ledger/null_ledger.ml
@@ -95,6 +95,8 @@ end = struct
   let set_at_index_exn _t =
     failwith "set_at_index_exn: null ledgers cannot be mutated"
 
+  let get_at_index _t _index = None
+
   let get_at_index_exn _t = failwith "get_at_index_exn: null ledgers are empty"
 
   let set_batch ?hash_cache:_ _t =
@@ -130,6 +132,8 @@ end = struct
 
   let tokens _t _pk = Token_id.Set.empty
 
+  let iteri_untrusted _t ~f:_ = ()
+
   let iteri _t ~f:_ = ()
 
   let fold_until _t ~init ~f:_ ~finish = Async.Deferred.return @@ finish init
diff --git a/src/lib/merkle_ledger/test/test_converting.ml b/src/lib/merkle_ledger/test/test_converting.ml
index f849717d2e8b..905a02d347ab 100644
--- a/src/lib/merkle_ledger/test/test_converting.ml
+++ b/src/lib/merkle_ledger/test/test_converting.ml
@@ -207,6 +207,59 @@ struct
                     [%test_eq: Migrated.Account.t] stored_migrated_account
                       (Db_converting.convert primary_account) ) ) ) )
 
+  let () =
+    add_test
+      "sync detection fails without crashing after accounts are added at high \
+       addresses" (fun () ->
+        with_primary ~f:(fun primary ->
+            let depth = Db.depth primary in
+            let max_height = Int.min 5 depth - 1 in
+            populate_primary_db primary max_height ;
+            with_migrated ~f:(fun migrated ->
+                let _converting =
+                  Db_converting.of_ledgers_with_migration primary migrated
+                in
+                let additional_account = Quickcheck.random_value Account.gen in
+                let high_index = (1 lsl Int.min 5 depth) - 1 in
+                let additional_account_addr =
+                  Db.Addr.of_int_exn ~ledger_depth:depth high_index
+                in
+                (* Using set_batch_accounts with a high address like this leaves
+                   the databases in an inconsistent state, because it updates
+                   the last added account in the databases but doesn't fill in
+                   the accounts at lower addresses. This state is similar to
+                   what you might get after an incomplete ledger sync. *)
+                Db.set_batch_accounts primary
+                  [ (additional_account_addr, additional_account) ] ;
+                Db_migrated.set_batch_accounts migrated
+                  [ ( additional_account_addr
+                    , Db_converting.convert additional_account )
+                  ] ;
+                assert (Db_converting.dbs_synced primary migrated) ) ) )
+
+  let () =
+    add_test "sync detection fails after converting ledger account is mutated"
+      (fun () ->
+        with_primary ~f:(fun primary ->
+            let depth = Db.depth primary in
+            let max_height = Int.min 5 depth in
+            populate_primary_db primary max_height ;
+            let account_to_mutate = Db.get_at_index_exn primary 0 in
+            let new_balance, _overflow_flag =
+              Balance.add_amount_flagged account_to_mutate.balance
+                Currency.Amount.one
+            in
+            let mutated_account =
+              Db_converting.convert
+                { account_to_mutate with balance = new_balance }
+            in
+            with_migrated ~f:(fun migrated ->
+                let _converting =
+                  Db_converting.of_ledgers_with_migration primary migrated
+                in
+                Db_migrated.set_at_index_exn migrated 0 mutated_account ;
+                assert (not (Db_converting.dbs_synced primary migrated)) ) ) )
+
   let () =
     add_test "create converting ledger, populate randomly, test iteration order"
       (fun () ->
diff --git a/src/lib/merkle_mask/masking_merkle_tree.ml b/src/lib/merkle_mask/masking_merkle_tree.ml
index 4fd9eddfd628..0f2170f3e0e4 100644
--- a/src/lib/merkle_mask/masking_merkle_tree.ml
+++ b/src/lib/merkle_mask/masking_merkle_tree.ml
@@ -879,10 +879,15 @@ module Make (Inputs : Inputs_intf.S) = struct
       let addr = Location.to_path_exn location in
       Addr.to_int addr
 
-    let get_at_index_exn t index =
+    let get_at_index t index =
       assert_is_attached t ;
       let addr = Addr.of_int_exn ~ledger_depth:t.depth index in
-      get t (Location.Account addr) |> Option.value_exn
+      get t (Location.Account addr)
+
+    let get_at_index_exn t index =
+      assert_is_attached t ;
+      get_at_index t index
+      |> Option.value_exn ~message:"Expected account at index" ~here:[%here]
 
     let set_at_index_exn t index account =
       assert_is_attached t ;
@@ -906,11 +911,17 @@ module Make (Inputs : Inputs_intf.S) = struct
       let%map.Async.Deferred accts = to_list t in
       List.map accts ~f:Account.identifier |> Account_id.Set.of_list
 
-    let iteri t ~f =
+    let iteri_untrusted t ~f =
       assert_is_attached t ;
       let num_accounts = num_accounts t in
       Sequence.range ~stop:`exclusive 0 num_accounts
-      |> Sequence.iter ~f:(fun i -> f i (get_at_index_exn t i))
+      |> Sequence.iter ~f:(fun i -> f i (get_at_index t i))
+
+    let iteri t ~f =
+      iteri_untrusted t ~f:(fun index account_opt ->
+          f index
+            (Option.value_exn ~message:"Expected account at index" ~here:[%here]
+               account_opt ) )
 
     let foldi_with_ignored_accounts t ignored_accounts ~init ~f =
       assert_is_attached t ;