diff --git a/lib/archethic/contracts/contract/constants.ex b/lib/archethic/contracts/contract/constants.ex
index ea98a6308..3a73ddad0 100644
--- a/lib/archethic/contracts/contract/constants.ex
+++ b/lib/archethic/contracts/contract/constants.ex
@@ -23,6 +23,7 @@ defmodule Archethic.Contracts.ContractConstants do
 
   @doc """
   Extract constants from a transaction into a map
+  This is a destructive operation. Some fields are not present in the resulting map.
   """
   @spec from_transaction(Transaction.t()) :: map()
   def from_transaction(%Transaction{
@@ -98,7 +99,7 @@ defmodule Archethic.Contracts.ContractConstants do
   def to_transaction(constants) do
     %Transaction{
       address: Map.get(constants, "address"),
-      type: Map.get(constants, "type"),
+      type: String.to_existing_atom(Map.get(constants, "type")),
       data: %TransactionData{
         code: Map.get(constants, "code", ""),
         content: Map.get(constants, "content", ""),
diff --git a/test/archethic/contracts/contract/constants_test.exs b/test/archethic/contracts/contract/constants_test.exs
new file mode 100644
index 000000000..0e93a911a
--- /dev/null
+++ b/test/archethic/contracts/contract/constants_test.exs
@@ -0,0 +1,28 @@
+defmodule Archethic.Contracts.ContractConstantsTest do
+  use ArchethicCase
+
+  alias Archethic.TransactionFactory
+  alias Archethic.TransactionChain.Transaction
+  alias Archethic.Contracts.ContractConstants
+
+  test "from_transaction/1 should return a map" do
+    tx = TransactionFactory.create_valid_transaction()
+
+    constant =
+      tx
+      |> ContractConstants.from_transaction()
+
+    assert %{"type" => "transfer"} = constant
+  end
+
+  test "to_transaction/1 should return a transaction" do
+    tx = TransactionFactory.create_valid_transaction()
+
+    # from_transaction/1 is a destructive function, we can't check
+    # that result is equal to tx
+    assert %Transaction{type: :transfer} =
+             tx
+             |> ContractConstants.from_transaction()
+             |> ContractConstants.to_transaction()
+  end
+end