diff --git a/IPython/core/guarded_eval.py b/IPython/core/guarded_eval.py
index c2d88d0..d60a5c5 100644
--- a/IPython/core/guarded_eval.py
+++ b/IPython/core/guarded_eval.py
@@ -60,7 +60,8 @@ MayHaveGetattr = Union[HasGetAttr, DoesNotHaveGetAttr]
 def _unbind_method(func: Callable) -> Union[Callable, None]:
     """Get unbound method for given bound method.
 
-    Returns None if cannot get unbound method."""
+    Returns None if cannot get unbound method, or method is already unbound.
+    """
     owner = getattr(func, "__self__", None)
     owner_class = type(owner)
     name = getattr(func, "__name__", None)
@@ -214,7 +215,7 @@ class SelectivePolicy(EvaluationPolicy):
 
         accept = False
 
-        # Many objects do not have `__getattr__`, this is fine
+        # Many objects do not have `__getattr__`, this is fine.
         if has_original_attr is None and has_original_attribute:
             accept = True
         else:
@@ -234,9 +235,10 @@ class SelectivePolicy(EvaluationPolicy):
             if not is_property:
                 return True
 
-            # Properties in allowed types are ok
+            # Properties in allowed types are ok (although we do not include any
+            # properties in our default allow list currently).
             if type(value) in self.allowed_getattr:
-                return True
+                return True  # pragma: no cover
 
             # Properties in subclasses of allowed types may be ok if not changed
             for module_name, *access_path in self.allowed_getattr_external:
diff --git a/IPython/core/tests/test_guarded_eval.py b/IPython/core/tests/test_guarded_eval.py
index 1ee93ff..905cf3a 100644
--- a/IPython/core/tests/test_guarded_eval.py
+++ b/IPython/core/tests/test_guarded_eval.py
@@ -22,7 +22,6 @@ unsafe = partial(create_context, "unsafe")
 dangerous = partial(create_context, "dangerous")
 
 LIMITED_OR_HIGHER = [limited, unsafe, dangerous]
-
 MINIMAL_OR_HIGHER = [minimal, *LIMITED_OR_HIGHER]
 
 
@@ -41,6 +40,39 @@ def module_not_installed(module: str):
         sys.modules[module] = to_restore
 
 
+def test_external_not_installed():
+    """
+    Because attribute check requires checking if object is not of allowed
+    external type, this tests logic for absence of external module.
+    """
+
+    class Custom:
+        def __init__(self):
+            self.test = 1
+
+        def __getattr__(self, key):
+            return key
+
+    with module_not_installed("pandas"):
+        context = limited(x=Custom())
+        with pytest.raises(GuardRejection):
+            guarded_eval("x.test", context)
+
+
+@dec.skip_without("pandas")
+def test_external_changed_api(monkeypatch):
+    """Check that the execution rejects if external API changed paths"""
+    import pandas as pd
+
+    series = pd.Series([1], index=["a"])
+
+    with monkeypatch.context() as m:
+        m.delattr(pd, "Series")
+        context = limited(data=series)
+        with pytest.raises(GuardRejection):
+            guarded_eval("data.iloc[0]", context)
+
+
 @dec.skip_without("pandas")
 def test_pandas_series_iloc():
     import pandas as pd
@@ -496,6 +528,7 @@ def test_unbind_method():
     x = X()
     assert _unbind_method(x.index) is X.index
     assert _unbind_method([].index) is list.index
+    assert _unbind_method(list.index) is None
 
 
 def test_assumption_instance_attr_do_not_matter():