diff --git a/src/endpoints/campaigns/get_free_domain.rs b/src/endpoints/campaigns/get_free_domain.rs
index 14319de..4a10920 100644
--- a/src/endpoints/campaigns/get_free_domain.rs
+++ b/src/endpoints/campaigns/get_free_domain.rs
@@ -131,11 +131,11 @@ pub async fn handler(
                                     "freeTx": 1,
                                     "whitelistedCalls": [
                                         {
-                                            "contractAddress": starknet_id_contract,
+                                            "contractAddress": to_hex(starknet_id_contract),
                                             "entrypoint": "*"
                                         },
                                         {
-                                            "contractAddress": free_domain_contract,
+                                            "contractAddress": to_hex(free_domain_contract),
                                             "entrypoint": "*"
                                         }
                                     ]