diff --git a/injector/__init__.py b/injector/__init__.py
index 0e79b22..731c1c1 100644
--- a/injector/__init__.py
+++ b/injector/__init__.py
@@ -1190,7 +1190,20 @@ def _infer_injected_bindings(callable: Callable, only_explicit_bindings: bool) -
             # mypy complains about this construct:
             #     error: The type alias is invalid in runtime context
             # See: https://github.com/python/mypy/issues/5354
-            bindings[k] = new_union  # type: ignore
+            union_metadata = {
+                metadata
+                for member in new_members
+                for metadata in getattr(member, '__metadata__', tuple())
+                if _is_specialization(member, Annotated)
+            }
+            if (
+                only_explicit_bindings
+                and _inject_marker not in union_metadata
+                or _noinject_marker in union_metadata
+            ):
+                del bindings[k]
+            else:
+                bindings[k] = new_union  # type: ignore
 
     return bindings
 
diff --git a/injector_test.py b/injector_test.py
index 9e3a601..76e9bd2 100644
--- a/injector_test.py
+++ b/injector_test.py
@@ -11,7 +11,7 @@
 """Functional tests for the "Injector" dependency injection framework."""
 
 from contextlib import contextmanager
-from typing import Any, NewType
+from typing import Any, NewType, Optional
 import abc
 import sys
 import threading
@@ -1481,3 +1481,16 @@ def test_get_bindings():
         pass
 
     assert get_bindings(function8) == {}
+
+    # Default arguments to NoInject annotations should behave the same as noninjectable decorator w.r.t 'None'
+    @inject
+    @noninjectable('b')
+    def function9(self, a: int, b: Optional[str] = None):
+        pass
+
+    @inject
+    def function10(self, a: int, b: NoInject[Optional[str]] = None):
+        # b:s type is Union[NoInject[Union[str, None]], None]
+        pass
+
+    assert get_bindings(function9) == {'a': int} == get_bindings(function10)