diff --git a/macropy/case_classes.py b/macropy/case_classes.py
index 899c2a45..d4d1551b 100644
--- a/macropy/case_classes.py
+++ b/macropy/case_classes.py
@@ -171,6 +171,7 @@ def prep_initialization(init_fun, args, vararg, kwarg, defaults, all_args):
     kws.update({
         'kwonlyargs': [],
         'kw_defaults': [],
+        'posonlyargs': [],
         'args': [ast.arg('self', None)] + [ast.arg(id, None) for id
                                            in args],
         'vararg': ast.arg(vararg, None) if vararg is not None else None,
@@ -235,7 +236,14 @@ def case_transform(tree, gen_sym, parents):
     tree.bases = parents
     assign = ast.FunctionDef(
         gen_sym("prepare_"+tree.name),
-        ast.arguments([], None, [], [], None, []),
+        ast.arguments(
+            posonlyargs=[],
+            args=[],
+            vararg=None,
+            kwonlyargs=[],
+            kw_defaults=[],
+            kwarg=None,
+            defaults=[]),
         outer,
         [hq[apply]],
         None
diff --git a/macropy/core/failure.py b/macropy/core/failure.py
index 6eeff151..a75df0b5 100644
--- a/macropy/core/failure.py
+++ b/macropy/core/failure.py
@@ -24,7 +24,7 @@ def clear_errors(tree, **kw):
         tb = "".join(traceback.format_tb(tree.__traceback__))
         msg = str(tree)
         if type(tree) is not AssertionError or tree.args == ():
-            msg = ("".join(tree.args) + "\nCaused by Macro-Expansion Error:\n" +
+            msg = ("".join(map(str, tree.args)) + "\nCaused by Macro-Expansion Error:\n" +
                    tb)
         return hq[raise_error(MacroExpansionError(msg))]
     else:
diff --git a/macropy/core/hquotes.py b/macropy/core/hquotes.py
index bd215baf..e053d366 100644
--- a/macropy/core/hquotes.py
+++ b/macropy/core/hquotes.py
@@ -132,8 +132,16 @@ def hygienator(tree, stop, scope, **kw):
         id, subtree = res
         if 'unhygienic' == id:
             stop()
-            tree.slice.value.ctx = None
-            return tree.slice.value
+            if isinstance(tree.slice, ast.Index):
+                # Python 3.8-
+                tree.slice.value.ctx = None
+                return tree.slice.value
+            elif isinstance(tree.slice, ast.expr):
+                # Python 3.9+
+                tree.slice.ctx = None
+                return tree.slice
+            else:
+                assert False, f'Wrong type: {type(tree.slice)}'
 
 
 macros.expose_unhygienic(ast)
diff --git a/macropy/core/macros.py b/macropy/core/macros.py
index 4127ead8..f0cd7ee8 100644
--- a/macropy/core/macros.py
+++ b/macropy/core/macros.py
@@ -105,11 +105,18 @@ class Expr(MacroType):
     brackets, like ``amacro[foo]``."""
 
     def detect_macro(self, in_tree):
-        if (isinstance(in_tree, ast.Subscript) and
-            type(in_tree.slice) is ast.Index):  # noqa: E129
-            body_tree = in_tree.slice.value
+        if isinstance(in_tree, ast.Subscript):
             name, macro_tree, call_args = self.get_macro_details(in_tree.value)
             if name is not None and name in self.registry:
+                if type(in_tree.slice) is ast.Index:
+                    # Python 3.8-
+                    body_tree = in_tree.slice.value
+                elif isinstance(in_tree.slice, ast.expr):
+                    # Python 3.8+
+                    body_tree = in_tree.slice
+                else:
+                    assert False, f'Wrong type: {type(in_tree.slice)}'
+
                 new_tree = yield MacroData(self.registry[name], macro_tree,
                                            body_tree, call_args, {}, name)
                 assert isinstance(new_tree, ast.expr), ('Wrong type %r' %
@@ -117,6 +124,7 @@ def detect_macro(self, in_tree):
                 new_tree = ast.Expr(new_tree)
 
 
+
 class Block(MacroType):
     """Handles block macros, defined by using a ``with`` statement, like:
 
@@ -614,8 +622,12 @@ def detect_macros(tree, from_fullname, from_package=None, from_module=None):
                 if name.name not in mod.macros.decorator.registry
             ]
 
+            # lineno and col_offset are required fields, so we set them to 0.
+            # If this causes issues we might consider setting them to the
+            # lineno following the last actual import, but this too might cause
+            # issues, since it might collide with existing code.
             stmt.names.extend([
-                ast.alias(x, x) for x in
+                ast.alias(x, x, lineno=0, col_offset=0) for x in
                 mod.macros.expose_unhygienic.registry.keys()
             ])
 
@@ -624,6 +636,11 @@ def detect_macros(tree, from_fullname, from_package=None, from_module=None):
 
 def check_annotated(tree):
     """Shorthand for checking if an AST is of the form something[...]."""
-    if (isinstance(tree, ast.Subscript) and type(tree.slice) is ast.Index and
-        type(tree.value) is ast.Name):  # noqa: E129
+    if not isinstance(tree, ast.Subscript) or type(tree.value) is not ast.Name:
+        return None
+    if type(tree.slice) is ast.Index:
+        # Python 3.8-
         return tree.value.id, tree.slice.value
+    elif isinstance(tree.slice, ast.expr):
+        # Python 3.9+
+        return tree.value.id, tree.slice