diff --git a/src/heros/__init__.py b/src/heros/__init__.py
index 43ce84b7e8565abc6700032da0872348616b17fb..fa0eae2c48604f2d988430dcf73643d5b5fd9358 100644
--- a/src/heros/__init__.py
+++ b/src/heros/__init__.py
@@ -1,4 +1,4 @@
-__version__ = "0.8.6"
+__version__ = "0.8.7"
 __proto_version__ = 1.0
 
 from .heros import HEROPeer, RemoteHERO, LocalHERO, EventObserver, HEROObserver
diff --git a/src/heros/capabilities.py b/src/heros/capabilities.py
index 9f360b570d6834c88a244b6396a40302bab5f32c..18f75e500841511fd6492a77d5fd344578b78ab0 100644
--- a/src/heros/capabilities.py
+++ b/src/heros/capabilities.py
@@ -13,7 +13,7 @@ if typing.TYPE_CHECKING:
     from zenoh import Query
 
 
-def type_to_str(annotation) -> str:
+def type_to_str(annotation: type | str) -> str:
     """
     Transforms annotation given as `types` to strings.
 
@@ -24,7 +24,9 @@ def type_to_str(annotation) -> str:
         Annotation as string.
     """
     if annotation is not inspect.Parameter.empty:
-        if isinstance(annotation, UnionType):
+        if type(annotation) is str:
+            return annotation
+        elif isinstance(annotation, UnionType):
             return repr(annotation)
         else:
             return annotation.__name__