diff --git a/src/trio/_core/_asyncgens.py b/src/trio/_core/_asyncgens.py
index 1ec7b6471..89976d25e 100644
--- a/src/trio/_core/_asyncgens.py
+++ b/src/trio/_core/_asyncgens.py
@@ -25,6 +25,32 @@
     _ASYNC_GEN_SET = set
 
 
+@_core.disable_ki_protection
+def _finalize_without_ki_protection(
+    agen_name: str,
+    agen: AsyncGeneratorType[object, NoReturn],
+) -> None:
+    # Host has no finalizer.  Reimplement the default
+    # Python behavior with no hooks installed: throw in
+    # GeneratorExit, step once, raise RuntimeError if
+    # it doesn't exit.
+    closer = agen.aclose()
+    try:
+        # If the next thing is a yield, this will raise RuntimeError
+        # which we allow to propagate
+        closer.send(None)
+    except StopIteration:
+        pass
+    else:
+        # If the next thing is an await, we get here. Give a nicer
+        # error than the default "async generator ignored GeneratorExit"
+        raise RuntimeError(
+            f"Non-Trio async generator {agen_name!r} awaited something "
+            "during finalization; install a finalization hook to "
+            "support this, or wrap it in 'async with aclosing(...):'",
+        )
+
+
 @attrs.define(eq=False)
 class AsyncGenerators:
     # Async generators are added to this set when first iterated. Any
@@ -78,6 +104,7 @@ def finalize_in_trio_context(
                 # have hit it.
                 self.trailing_needs_finalize.add(agen)
 
+        @_core.enable_ki_protection
         def finalizer(agen: AsyncGeneratorType[object, NoReturn]) -> None:
             try:
                 self.foreign.remove(id(agen))
@@ -112,25 +139,7 @@ def finalizer(agen: AsyncGeneratorType[object, NoReturn]) -> None:
                 if self.prev_hooks.finalizer is not None:
                     self.prev_hooks.finalizer(agen)
                 else:
-                    # Host has no finalizer.  Reimplement the default
-                    # Python behavior with no hooks installed: throw in
-                    # GeneratorExit, step once, raise RuntimeError if
-                    # it doesn't exit.
-                    closer = agen.aclose()
-                    try:
-                        # If the next thing is a yield, this will raise RuntimeError
-                        # which we allow to propagate
-                        closer.send(None)
-                    except StopIteration:
-                        pass
-                    else:
-                        # If the next thing is an await, we get here. Give a nicer
-                        # error than the default "async generator ignored GeneratorExit"
-                        raise RuntimeError(
-                            f"Non-Trio async generator {agen_name!r} awaited something "
-                            "during finalization; install a finalization hook to "
-                            "support this, or wrap it in 'async with aclosing(...):'",
-                        )
+                    _finalize_without_ki_protection(agen_name, agen)
 
         self.prev_hooks = sys.get_asyncgen_hooks()
         sys.set_asyncgen_hooks(firstiter=firstiter, finalizer=finalizer)  # type: ignore[arg-type]  # Finalizer doesn't use AsyncGeneratorType