diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index dedfe3a..04634f3 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -25,6 +25,9 @@ jobs:
     - name: Run tests
       run: |
         pytest
+    - name: Lint with ruff
+      run: |
+        ruff check symbex
     - name: Check if cog needs to be run
       run: |
         cog README.md
diff --git a/README.md b/README.md
index bfa30bc..71c18e5 100644
--- a/README.md
+++ b/README.md
@@ -173,31 +173,31 @@ cog.out(
 )
 ]]] -->
 ```python
-# File: symbex/lib.py Line: 106
+# File: symbex/lib.py Line: 107
 def function_definition(function_node: AST)
 
 # File: symbex/lib.py Line: 13
 def find_symbol_nodes(code: str, filename: str, symbols: Iterable[str]) -> List[Tuple[(AST, Optional[str])]]
 
-# File: symbex/lib.py Line: 174
+# File: symbex/lib.py Line: 175
 def class_definition(class_def)
 
-# File: symbex/lib.py Line: 208
+# File: symbex/lib.py Line: 209
 def annotation_definition(annotation: AST) -> str
 
-# File: symbex/lib.py Line: 226
+# File: symbex/lib.py Line: 227
 def read_file(path)
 
-# File: symbex/lib.py Line: 252
+# File: symbex/lib.py Line: 253
 class TypeSummary
 
-# File: symbex/lib.py Line: 257
+# File: symbex/lib.py Line: 258
 def type_summary(node: AST) -> Optional[TypeSummary]
 
-# File: symbex/lib.py Line: 303
+# File: symbex/lib.py Line: 304
 def quoted_string(s)
 
-# File: symbex/lib.py Line: 314
+# File: symbex/lib.py Line: 315
 def import_line_for_function(function_name: str, filepath: str, possible_root_dirs: List[str]) -> str
 
 # File: symbex/lib.py Line: 37
@@ -206,7 +206,7 @@ def code_for_node(code: str, node: AST, class_name: str, signatures: bool, docst
 # File: symbex/lib.py Line: 71
 def add_docstring(definition: str, node: AST, docstrings: bool, is_method: bool) -> str
 
-# File: symbex/lib.py Line: 81
+# File: symbex/lib.py Line: 82
 def match(name: str, symbols: Iterable[str]) -> bool
 ```
 <!-- [[[end]]] -->
@@ -227,7 +227,7 @@ cog.out(
 )
 ]]] -->
 ```python
-# File: symbex/lib.py Line: 81
+# File: symbex/lib.py Line: 82
 # from symbex.lib import match
 def match(name: str, symbols: Iterable[str]) -> bool
 ```
@@ -265,7 +265,7 @@ cog.out(
 )
 ]]] -->
 ```python
-# File: symbex/lib.py Line: 81
+# File: symbex/lib.py Line: 82
 def match(name: str, symbols: Iterable[str]) -> bool
     "Returns True if name matches any of the symbols, resolving wildcards"
 ```
diff --git a/setup.py b/setup.py
index eaf4dea..f1d91a5 100644
--- a/setup.py
+++ b/setup.py
@@ -32,6 +32,6 @@ def get_long_description():
         symbex=symbex.cli:cli
     """,
     install_requires=["click"],
-    extras_require={"test": ["pytest", "pytest-icdiff", "cogapp", "PyYAML"]},
+    extras_require={"test": ["pytest", "pytest-icdiff", "cogapp", "PyYAML", "ruff"]},
     python_requires=">=3.8",
 )
diff --git a/symbex/cli.py b/symbex/cli.py
index dff0b36..d6a246c 100644
--- a/symbex/cli.py
+++ b/symbex/cli.py
@@ -232,7 +232,7 @@ def cli(
                     module_dirs.append(mod_path.parent)
                 else:
                     module_files.append(mod_path)
-            except ModuleNotFoundError as ex:
+            except ModuleNotFoundError:
                 raise click.ClickException("Module not found: {}".format(module))
         directories = [*directories, *module_dirs]
         files = [*files, *module_files]
@@ -318,10 +318,6 @@ def iterate_files():
                 if path.is_file():
                     yield path
 
-    # Filter symbols by type
-    def filter(node: ast.AST) -> bool:
-        return True
-
     # If any --filters were supplied, handle them:
     if any(
         [
@@ -337,7 +333,7 @@ def filter(node: ast.AST) -> bool:
             no_init,
         ]
     ):
-
+        # Return just nodes matching filters
         def filter(node: ast.AST) -> bool:
             # Filters must ALL match
             if async_ and not isinstance(node, ast.AsyncFunctionDef):
@@ -371,6 +367,11 @@ def filter(node: ast.AST) -> bool:
                 return False
             return True
 
+    else:
+        # All nodes are allowed
+        def filter(node: ast.AST) -> bool:
+            return True
+
     pwd = pathlib.Path(".").resolve()
     num_matches = 0
     replace_matches = []
diff --git a/symbex/lib.py b/symbex/lib.py
index e9ad1a4..3f17ccd 100644
--- a/symbex/lib.py
+++ b/symbex/lib.py
@@ -75,7 +75,8 @@ def add_docstring(definition: str, node: AST, docstrings: bool, is_method: bool)
     if not docstring:
         return definition
     docstring = quoted_string(docstring)
-    return f"{definition}\n{textwrap.indent(docstring, '        ' if is_method else '    ')}"
+    wrapped = textwrap.indent(docstring, "        " if is_method else "    ")
+    return f"{definition}\n{wrapped}"
 
 
 def match(name: str, symbols: Iterable[str]) -> bool:
diff --git a/tests/example_symbols.py b/tests/example_symbols.py
index b3a15f0..45e1044 100644
--- a/tests/example_symbols.py
+++ b/tests/example_symbols.py
@@ -1,4 +1,4 @@
-from typing import Union, Tuple
+from typing import Tuple
 
 
 # Function with no arguments