diff --git a/.github/workflows/test.yaml b/.github/workflows/test.yaml
index 00ed1b00..0368ba7b 100644
--- a/.github/workflows/test.yaml
+++ b/.github/workflows/test.yaml
@@ -23,6 +23,7 @@ jobs:
           sudo apt remove python3-pip
           python -m pip install --upgrade pip
           python -m pip install . black isort mypy pytest readme_renderer
+          python -m pip install . types-dataclasses  # Needed for Python 3.6
           pip list
       - name: Type Checker
         run: |
diff --git a/ptpython/repl.py b/ptpython/repl.py
index b158b93c..455e5f38 100644
--- a/ptpython/repl.py
+++ b/ptpython/repl.py
@@ -98,7 +98,7 @@ def run_and_show_expression(self, expression):
             except KeyboardInterrupt:  # KeyboardInterrupt doesn't inherit from Exception.
                 raise
             except SystemExit:
-                return
+                raise
             except BaseException as e:
                 self._handle_exception(e)
             else:
@@ -330,9 +330,7 @@ def _format_result_output(self, result: object) -> StyleAndTextTuples:
                 else:
                     result_repr = black.format_str(
                         result_repr,
-                        mode=black.FileMode(
-                            line_length=self.app.output.get_size().columns
-                        ),
+                        mode=black.Mode(line_length=self.app.output.get_size().columns),
                     )
 
             formatted_result_repr = to_formatted_text(