diff --git a/apps/explorer/lib/explorer/chain/import/runner/blocks.ex b/apps/explorer/lib/explorer/chain/import/runner/blocks.ex
index 9f24d0be7b..5917ae9968 100644
--- a/apps/explorer/lib/explorer/chain/import/runner/blocks.ex
+++ b/apps/explorer/lib/explorer/chain/import/runner/blocks.ex
@@ -133,6 +133,9 @@ defmodule Explorer.Chain.Import.Runner.Blocks do
     insert_sql = """
     INSERT INTO transaction_forks (uncle_hash, index, hash, inserted_at, updated_at)
     #{select_sql}
+    ON CONFLICT (uncle_hash, index)
+    DO UPDATE SET hash = EXCLUDED.hash
+    WHERE EXCLUDED.hash <> transaction_forks.hash
     RETURNING uncle_hash, hash
     """
 
diff --git a/apps/explorer/test/explorer/chain/import/runner/blocks_test.exs b/apps/explorer/test/explorer/chain/import/runner/blocks_test.exs
new file mode 100644
index 0000000000..cba86e999a
--- /dev/null
+++ b/apps/explorer/test/explorer/chain/import/runner/blocks_test.exs
@@ -0,0 +1,84 @@
+defmodule Explorer.Chain.Import.Runner.BlocksTest do
+  use Explorer.DataCase
+
+  import Ecto.Query, only: [from: 2, select: 2, where: 2]
+
+  alias Ecto.Multi
+  alias Explorer.Chain.Import.Runner.{Blocks, Transaction}
+  alias Explorer.Chain.{Block, Transaction}
+  alias Explorer.Repo
+
+  describe "run/1" do
+    setup do
+      block = insert(:block, consensus: true)
+
+      transaction =
+        :transaction
+        |> insert()
+        |> with_block(block)
+
+      %{consensus_block: block, transaction: transaction}
+    end
+
+    test "derive_transaction_forks replaces hash on conflicting (uncle_hash, index)", %{
+      consensus_block: %Block{hash: block_hash, miner_hash: miner_hash, number: block_number},
+      transaction: transaction
+    } do
+      block_params =
+        params_for(:block, hash: block_hash, miner_hash: miner_hash, number: block_number, consensus: false)
+
+      %Ecto.Changeset{valid?: true, changes: block_changes} = Block.changeset(%Block{}, block_params)
+      changes_list = [block_changes]
+
+      timestamp = DateTime.utc_now()
+      options = %{timestamps: %{inserted_at: timestamp, updated_at: timestamp}}
+
+      assert Repo.aggregate(from(transaction in Transaction, where: is_nil(transaction.block_number)), :count, :hash) ==
+               0
+
+      assert count(Transaction.Fork) == 0
+
+      # re-org consensus_block to uncle
+
+      assert {:ok, %{derive_transaction_forks: [_]}} =
+               Multi.new()
+               |> Blocks.run(changes_list, options)
+               |> Repo.transaction()
+
+      assert Repo.aggregate(where(Block, consensus: false), :count, :number) == 1
+
+      assert Repo.aggregate(from(transaction in Transaction, where: is_nil(transaction.block_number)), :count, :hash) ==
+               1
+
+      assert count(Transaction.Fork) == 1
+
+      non_consensus_transaction = Repo.get(Transaction, transaction.hash)
+      non_consensus_block = Repo.get(Block, block_hash)
+
+      # Make it consensus again
+      new_consensus_block =
+        non_consensus_block
+        |> Block.changeset(%{consensus: true})
+        |> Repo.update!()
+
+      with_block(non_consensus_transaction, new_consensus_block)
+
+      ctid = Repo.one!(from(transaction_fork in Transaction.Fork, select: "ctid"))
+
+      assert Repo.aggregate(from(transaction in Transaction, where: is_nil(transaction.block_number)), :count, :hash) ==
+               0
+
+      assert {:ok, %{derive_transaction_forks: []}} =
+               Multi.new()
+               |> Blocks.run(changes_list, options)
+               |> Repo.transaction()
+
+      assert Repo.one!(from(transaction_fork in Transaction.Fork, select: "ctid")) == ctid,
+             "Tuple was written even though it is not distinct"
+    end
+  end
+
+  defp count(schema) do
+    Repo.one!(select(schema, fragment("COUNT(*)")))
+  end
+end