diff --git a/src/black/parsing.py b/src/black/parsing.py
index 2a455bacb0d..c64cb505764 100644
--- a/src/black/parsing.py
+++ b/src/black/parsing.py
@@ -164,9 +164,13 @@ def _normalize(lineend: str, value: str) -> str:
 def stringify_ast(node: ast.AST, depth: int = 0) -> Iterator[str]:
     """Simple visitor generating strings to compare ASTs by content."""
 
+    if isinstance(node, ast.Constant) and isinstance(node.value, str) and node.kind == "u":
+        # It's a quirk of history that we strip the u prefix over here. We used to rewrite
+        # the AST nodes for Python version compatibility and we never copied over the kind
+        node.kind = None
+
     yield f"{'  ' * depth}{node.__class__.__name__}("
 
-    type_ignore_classes: Tuple[Type[Any], ...]
     for field in sorted(node._fields):  # noqa: F402
         # TypeIgnore has only one field 'lineno' which breaks this comparison
         if isinstance(node, ast.TypeIgnore):