diff --git a/.github/workflows/ci_cd.yml b/.github/workflows/ci_cd.yml
index 785ea389..e15299af 100644
--- a/.github/workflows/ci_cd.yml
+++ b/.github/workflows/ci_cd.yml
@@ -54,6 +54,7 @@ jobs:
       - uses: ansys/actions/tests-pytest@v5
         with:
           pytest-extra-args: "--cov=ansys.pre_commit_hooks --cov-report=term --cov-report=html:.cov/html"
+          python-version: ${{ matrix.python-version }}
 
   doc-build:
     name: "Build documentation"
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 30b73589..397cacec 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -41,6 +41,13 @@ repos:
     - id: check-github-workflows
 
 - repo: https://github.com/ansys/pre-commit-hooks
-  rev: v0.2.4
-  hooks:
-  - id: add-license-headers
\ No newline at end of file
+  rev: v0.2.6
+  hooks:
+  - id: add-license-headers
+    args:
+    - --start_year=2023
+    exclude: |
+        (?x)^(
+            tests/test_reuse_files/bad_chars.py |
+            tests/test_reuse_files/index_error.scss
+        )$
\ No newline at end of file
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 56321513..fb9ed93d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,12 @@
 
 This document follows the conventions laid out in [Keep a CHANGELOG](https://keepachangelog.com/en/1.0.0).
 
+## [Unreleased]()
+
+### Fixed
+
+- Fix pytest python versions and fileinput [#118](https://github.com/ansys/pre-commit-hooks/pull/118)
+
 ## [0.2.6](https://github.com/ansys/pre-commit-hooks/releases/tag/v0.2.6) - January 11 2024
 
 ### Added
diff --git a/src/ansys/pre_commit_hooks/add_license_headers.py b/src/ansys/pre_commit_hooks/add_license_headers.py
index 30bae08a..dccdfdc1 100644
--- a/src/ansys/pre_commit_hooks/add_license_headers.py
+++ b/src/ansys/pre_commit_hooks/add_license_headers.py
@@ -32,6 +32,7 @@
 import json
 import os
 import pathlib
+from platform import python_version
 import shutil
 import sys
 from tempfile import NamedTemporaryFile
@@ -382,10 +383,17 @@ def add_hook_changes(before_hook: str, after_hook: str) -> None:
     before_hook_lines = before_hook_file.readlines()
     found_reuse_info = False
 
+    # Check if python version is 3.9 since fileinput.input()
+    # does not support the "encoding" keyword
+    if "3.9" in python_version():
+        file = fileinput.input(after_hook, inplace=True)
+    else:
+        file = fileinput.input(after_hook, inplace=True, encoding="utf8")
+
     # Copy file content before add-license-header was run into
     # the file after add-license-header was run.
     # stdout is redirected into the file if inplace is True
-    for line in fileinput.input(after_hook, inplace=True, encoding="utf8"):
+    for line in file:
         # Copy the new reuse lines into the file
         if _util.contains_reuse_info(line):
             count += 1
diff --git a/test-repo b/test-repo
new file mode 160000
index 00000000..a59a0587
--- /dev/null
+++ b/test-repo
@@ -0,0 +1 @@
+Subproject commit a59a0587ae6746ae9e8eca1780d8176ea933a4e7
diff --git a/tests/test_reuse.py b/tests/test_reuse.py
index 125c9ba4..87f4ebf2 100644
--- a/tests/test_reuse.py
+++ b/tests/test_reuse.py
@@ -58,12 +58,12 @@ def set_up_repo(tmp_path, template_path, template_name, license_path, license_na
 
 def make_asset_dirs(tmp_path, template_path, template_name, license_path, license_name):
     """Make asset directories if using a custom license or template."""
-    if "ansys" not in template_name:
+    if template_name != "ansys.jinja2":
         reuse_dir = os.path.join(tmp_path, ".reuse", "templates")
         os.makedirs(reuse_dir)
         shutil.copyfile(template_path, f"{reuse_dir}/{template_name}")
 
-    if "MIT" not in license_name:
+    if license_name != "MIT.txt":
         license_dir = os.path.join(tmp_path, "LICENSES")
         os.makedirs(license_dir)
         shutil.copyfile(license_path, f"{license_dir}/{license_name}")
@@ -96,7 +96,7 @@ def add_argv_run(repo, tmp_file, custom_args):
 
 def check_ansys_header(file_name):
     """Check file contains all copyright and license header components."""
-    file = open(file_name, "r")
+    file = open(file_name, "r", encoding="utf8")
     count = 0
     for line in file:
         count += 1
@@ -175,8 +175,8 @@ def test_custom_args(tmp_path: pytest.TempPathFactory):
     # Set template and license names
     template_name = "test_template.jinja2"
     license_name = "ECL-1.0.txt"
-    template_path = os.path.join(REPO_PATH, "tests", "templates", template_name)
-    license_path = os.path.join(REPO_PATH, "tests", "LICENSES", license_name)
+    template_path = os.path.join(REPO_PATH, "tests", "test_reuse_files", "templates", template_name)
+    license_path = os.path.join(REPO_PATH, "tests", "test_reuse_files", "LICENSES", license_name)
 
     # Set up git repository in tmp_path with temporary file
     repo, tmp_file = set_up_repo(tmp_path, template_path, template_name, license_path, license_name)
@@ -291,7 +291,7 @@ def test_no_license_check(tmp_path: pytest.TempPathFactory):
     # Set template and license names
     template_name = "copyright_only.jinja2"
     license_name = "MIT.txt"
-    template_path = os.path.join(REPO_PATH, "tests", "templates", template_name)
+    template_path = os.path.join(REPO_PATH, "tests", "test_reuse_files", "templates", template_name)
     license_path = os.path.join(REPO_PATH, "LICENSES", license_name)
 
     # Set up git repository in tmp_path with temporary file
@@ -364,8 +364,8 @@ def test_update_changed_header(tmp_path: pytest.TempPathFactory):
     # Set template and license names
     template_name = "test_template.jinja2"
     license_name = "ECL-1.0.txt"
-    template_path = os.path.join(REPO_PATH, "tests", "templates", template_name)
-    license_path = os.path.join(REPO_PATH, "tests", "LICENSES", license_name)
+    template_path = os.path.join(REPO_PATH, "tests", "test_reuse_files", "templates", template_name)
+    license_path = os.path.join(REPO_PATH, "tests", "test_reuse_files", "LICENSES", license_name)
 
     # Set up git repository in tmp_path with temporary file
     repo, tmp_file = set_up_repo(tmp_path, template_path, template_name, license_path, license_name)
@@ -425,8 +425,8 @@ def test_missing_licenses(tmp_path: pytest.TempPathFactory):
     # Set template and license names
     template_name = "test_template.jinja2"
     license_name = "ECL-1.0.txt"
-    template_path = os.path.join(REPO_PATH, "tests", "templates", template_name)
-    license_path = os.path.join(REPO_PATH, "tests", "LICENSES", license_name)
+    template_path = os.path.join(REPO_PATH, "tests", "test_reuse_files", "templates", template_name)
+    license_path = os.path.join(REPO_PATH, "tests", "test_reuse_files", "LICENSES", license_name)
 
     # Set up git repository in tmp_path with temporary file
     repo, tmp_file = set_up_repo(tmp_path, template_path, template_name, license_path, license_name)
@@ -496,3 +496,95 @@ def test_copy_assets(tmp_path: pytest.TempPathFactory):
     assert add_argv_run(repo, new_files, new_files) == 1
 
     check_ansys_header(tmp_file)
+
+
+def test_bad_chars(tmp_path: pytest.TempPathFactory):
+    # Set template and license names
+    template_name = "ansys.jinja2"
+    license_name = "MIT.txt"
+    bad_chars_name = "bad_chars.py"
+    template_path = os.path.join(REPO_PATH, ".reuse", "templates", template_name)
+    license_path = os.path.join(REPO_PATH, "LICENSES", license_name)
+
+    # Change dir to tmp_path
+    os.chdir(tmp_path)
+
+    # Make asset directories if using a custom license or template
+    # Asset directories are .reuse and LICENSES
+    make_asset_dirs(tmp_path, template_path, template_name, license_path, license_name)
+
+    # Set up git repository in tmp_path
+    git.Repo.init(tmp_path)
+    repo = git.Repo(tmp_path)
+    repo.index.commit("initialized git repo for tmp_path")
+
+    # Copy file with bad characters to git repository
+    shutil.copyfile(
+        os.path.join(REPO_PATH, "tests", "test_reuse_files", bad_chars_name), bad_chars_name
+    )
+
+    # Assert the hook failed
+    assert add_argv_run(repo, bad_chars_name, [bad_chars_name]) == 1
+
+    # Assert the hook added the license header correctly
+    check_ansys_header(bad_chars_name)
+
+    os.chdir(REPO_PATH)
+
+
+def test_index_exception(tmp_path: pytest.TempPathFactory):
+    # Set template and license names
+    template_name = "copyright_only.jinja2"
+    license_name = "MIT.txt"
+    test_filename = "index_error.scss"
+    template_path = os.path.join(REPO_PATH, "tests", "test_reuse_files", "templates", template_name)
+    license_path = os.path.join(REPO_PATH, "LICENSES", license_name)
+
+    # Change dir to tmp_path
+    os.chdir(tmp_path)
+
+    # Make asset directories if using a custom license or template
+    # Asset directories are .reuse and LICENSES
+    make_asset_dirs(tmp_path, template_path, template_name, license_path, license_name)
+
+    # Set up git repository in tmp_path
+    git.Repo.init(tmp_path)
+    repo = git.Repo(tmp_path)
+    repo.index.commit("initialized git repo for tmp_path")
+
+    # Copy file that will cause an IndexError to git repository
+    shutil.copyfile(
+        os.path.join(REPO_PATH, "tests", "test_reuse_files", test_filename), test_filename
+    )
+
+    custom_args = [
+        test_filename,
+        "--custom_template=copyright_only",
+        "--custom_copyright=ANSYS, Inc. Unauthorized use, distribution, \
+            or duplication is prohibited.",
+        "--ignore_license_check",
+        "--start_year=2023",
+    ]
+
+    # Assert the hook failed
+    assert add_argv_run(repo, test_filename, custom_args) == 1
+
+    # Assert the single line comment changed to
+    # a multiline comment. This causes an IndexError in the hook
+    file = open(test_filename, "r")
+    count = 0
+    for line in file:
+        count += 1
+        if count == 1:
+            assert "/*" in line
+        # Ensure header was updated correctly and didn't add
+        # an extra SPDX-Identifier line
+        if count == 2:
+            assert f" * Copyright (C) 2023 - {dt.today().year} ANSYS, Inc. Unauthorized use" in line
+        if count == 3:
+            assert "*/" in line
+        if count > 4:
+            break
+    file.close()
+
+    os.chdir(REPO_PATH)
diff --git a/tests/LICENSES/ECL-1.0.txt b/tests/test_reuse_files/LICENSES/ECL-1.0.txt
similarity index 100%
rename from tests/LICENSES/ECL-1.0.txt
rename to tests/test_reuse_files/LICENSES/ECL-1.0.txt
diff --git a/tests/test_reuse_files/bad_chars.py b/tests/test_reuse_files/bad_chars.py
new file mode 100644
index 00000000..319368ba
--- /dev/null
+++ b/tests/test_reuse_files/bad_chars.py
@@ -0,0 +1,4 @@
+"""Test if fileinput.input() in add-license-headers decodes bad characters."""
+# This intentionally does not have a header, so we can test the
+# license header is added in test_reuse.py - test_bad_chars()
+print("ÞĀĂĄĆĈĊČĎĐĒĔĖĘĚĜĞĠĢĤĦĨĪĬĮİIJĴ")
diff --git a/tests/test_reuse_files/index_error.scss b/tests/test_reuse_files/index_error.scss
new file mode 100644
index 00000000..ef3378b9
--- /dev/null
+++ b/tests/test_reuse_files/index_error.scss
@@ -0,0 +1,2 @@
+// Copyright (C) 2023 ANSYS, Inc. Unauthorized use, distribution, or duplication is prohibited.
+// This tests the before_hook index exception in add-license-headers.
\ No newline at end of file
diff --git a/tests/templates/copyright_only.jinja2 b/tests/test_reuse_files/templates/copyright_only.jinja2
similarity index 100%
rename from tests/templates/copyright_only.jinja2
rename to tests/test_reuse_files/templates/copyright_only.jinja2
diff --git a/tests/templates/test_template.jinja2 b/tests/test_reuse_files/templates/test_template.jinja2
similarity index 100%
rename from tests/templates/test_template.jinja2
rename to tests/test_reuse_files/templates/test_template.jinja2