diff --git a/hathor/nanocontracts/resources/blueprint.py b/hathor/nanocontracts/resources/blueprint.py
index bf6f9d5ed..f2626cb94 100644
--- a/hathor/nanocontracts/resources/blueprint.py
+++ b/hathor/nanocontracts/resources/blueprint.py
@@ -18,6 +18,7 @@
 import typing
 from typing import TYPE_CHECKING, Any, Optional
 
+import hathor
 from hathor._openapi.register import register_resource
 from hathor.api_util import Resource, set_cors
 from hathor.nanocontracts import types as nc_types
@@ -66,6 +67,8 @@ def get_type_name(self, type_: type) -> str:
                 match args:
                     case (_subtype, types.NoneType) | (types.NoneType, _subtype):
                         return self._get_optional_type_name(_subtype)
+                    case (hathor.Address, hathor.ContractId) | (hathor.ContractId, hathor.Address):
+                        return 'CallerId'
                 return self._get_composed_type_name('union', args)
             case nc_types.SignedData:
                 return self._get_composed_type_name('SignedData', args)
diff --git a/hathor_tests/resources/nanocontracts/my_blueprint.py b/hathor_tests/resources/nanocontracts/my_blueprint.py
index e98e56a8e..a8d614711 100644
--- a/hathor_tests/resources/nanocontracts/my_blueprint.py
+++ b/hathor_tests/resources/nanocontracts/my_blueprint.py
@@ -4,6 +4,7 @@
     Address,
     Amount,
     Blueprint,
+    CallerId,
     Context,
     SignedData,
     Timestamp,
@@ -30,6 +31,7 @@ class MyBlueprint(Blueprint):
     a_tuple: tuple[str, int, bool]
     a_dict_dict_tuple: dict[str, tuple[str, int]]
     a_optional_int: Optional[int]
+    a_caller_id: CallerId
 
     @public
     def initialize(self, ctx: Context, arg1: int) -> None:
diff --git a/hathor_tests/resources/nanocontracts/test_blueprint.py b/hathor_tests/resources/nanocontracts/test_blueprint.py
index 7ed434c9c..71d55945c 100644
--- a/hathor_tests/resources/nanocontracts/test_blueprint.py
+++ b/hathor_tests/resources/nanocontracts/test_blueprint.py
@@ -71,6 +71,7 @@ def test_success(self) -> Generator[Deferred[Any], Any, None]:
             'a_tuple': 'tuple[str, int, bool]',
             'a_dict_dict_tuple': 'dict[str, tuple[str, int]]',
             'a_optional_int': 'int?',
+            'a_caller_id': 'CallerId',
         })
         self.assertEqual(data['public_methods'], {
             'initialize': {