diff --git a/pre_commit_hooks/pretty_format_json.py b/pre_commit_hooks/pretty_format_json.py
index a9738df..2fdc173 100644
--- a/pre_commit_hooks/pretty_format_json.py
+++ b/pre_commit_hooks/pretty_format_json.py
@@ -8,11 +8,14 @@ from collections.abc import Mapping
 from collections.abc import Sequence
 from difflib import unified_diff
 
+
 def _insert_linebreaks(json_str: str) -> str:
     return re.sub(
-        r'\n(?P<spaces>\s*)(?P<json_key>.*): {}(?P<delim>,??)', 
-        '\n\g<spaces>\g<json_key>: {\n\g<spaces>}\g<delim>', 
-        json_str)
+        r'\n(?P<spaces>\s*)(?P<json_key>.*): {}(?P<delim>,??)',
+        '\n\\g<spaces>\\g<json_key>: {\n\\g<spaces>}\\g<delim>',
+        json_str,
+    )
+
 
 def _get_pretty_format(
         contents: str,
@@ -110,8 +113,8 @@ def main(argv: Sequence[str] | None = None) -> int:
         action='store_true',
         dest='empty_object_with_newline',
         default=False,
-        help='Format empty JSON objects to have a linebreak, ' \
-            + 'also activates --no-sort-keys',
+        help='Format empty JSON objects to have a linebreak, ' +
+        'also activates --no-sort-keys',
     )
     parser.add_argument('filenames', nargs='*', help='Filenames to fix')
     args = parser.parse_args(argv)
@@ -150,7 +153,7 @@ def main(argv: Sequence[str] | None = None) -> int:
                     diff_output = get_diff(
                         contents,
                         pretty_contents,
-                        json_file
+                        json_file,
                     )
                     sys.stdout.buffer.write(diff_output.encode())
                     status = 1
diff --git a/tests/pretty_format_json_test.py b/tests/pretty_format_json_test.py
index 44884ad..4efbf0f 100644
--- a/tests/pretty_format_json_test.py
+++ b/tests/pretty_format_json_test.py
@@ -165,7 +165,7 @@ def test_empty_object_with_newline(tmpdir):
     assert ret == 1
 
     # a template to be compared against.
-    multiline = get_resource_path("empty_object_json_multiline.json")
+    multiline = get_resource_path('empty_object_json_multiline.json')
 
     # file has empty object with newline => expect fail with default settings
     ret = main([str(multiline)])
@@ -173,20 +173,22 @@ def test_empty_object_with_newline(tmpdir):
 
     # launch the autofix with empty object with newline support on that file
     to_be_formatted_sameline = tmpdir.join(
-        "not_pretty_formatted_empty_object_json_sameline.json"
+        'not_pretty_formatted_empty_object_json_sameline.json',
     )
     shutil.copyfile(str(sameline), str(to_be_formatted_sameline))
     ret = main(
-        ["--autofix",
-        "--empty-object-with-newline",
-        str(to_be_formatted_sameline)]
+        [
+            '--autofix',
+            '--empty-object-with-newline',
+            str(to_be_formatted_sameline),
+        ],
     )
     # it should have formatted it and don't raise an error code
     # to not stop the the commit
     assert ret == 0
 
-    # file was formatted (shouldn't trigger linter with 
+    # file was formatted (shouldn't trigger linter with
     # --empty-object-with-newline switch)
-    ret = main(["--empty-object-with-newline", str(to_be_formatted_sameline)])
+    ret = main(['--empty-object-with-newline', str(to_be_formatted_sameline)])
     assert ret == 0
     assert filecmp.cmp(to_be_formatted_sameline, multiline)