diff --git a/src/black/__init__.py b/src/black/__init__.py
index 405a01082e7..d201ce55cb7 100644
--- a/src/black/__init__.py
+++ b/src/black/__init__.py
@@ -1315,7 +1315,10 @@ def assert_equivalent(src: str, dst: str, *, pass_num: int = 1) -> None:
         src_ast = parse_ast(src)
     except Exception as exc:
         raise AssertionError(
-            f"cannot use --safe with this file; failed to parse source file: {exc}"
+            f"cannot use --safe with this file; failed to parse source file AST: "
+            f"{exc}\n"
+            f"This could be caused by running Black with an older Python version "
+            f"that does not support new syntax used in your source file."
         ) from exc
 
     try: