diff --git a/sphinx/transforms.py b/sphinx/transforms.py
index 49c0aba1e..4619449e7 100644
--- a/sphinx/transforms.py
+++ b/sphinx/transforms.py
@@ -121,13 +121,13 @@ class AutoNumbering(Transform):
                 if has_child(node, nodes.caption):
                     self.document.note_implicit_target(node)
             elif isinstance(node, nodes.image):
-                if has_child(node.parent, nodes.caption):
+                if node.parent and has_child(node.parent, nodes.caption):
                     self.document.note_implicit_target(node.parent)
             elif isinstance(node, nodes.table):
                 if has_child(node, nodes.title):
                     self.document.note_implicit_target(node)
             elif isinstance(node, nodes.literal_block):
-                if has_child(node.parent, nodes.caption):
+                if node.parent and has_child(node.parent, nodes.caption):
                     self.document.note_implicit_target(node.parent)