diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 96aeb72..bdea3bb 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -2,19 +2,18 @@ name: ci
 on: [push, pull_request]
 
 jobs:
+
   check-format:
+
     runs-on: ubuntu-latest
+
     steps:
     - uses: actions/checkout@v2
-    - uses: actions/setup-python@v2
+    - name: Set up Python 3.8
+      uses: actions/setup-python@v2
       with:
         python-version: 3.8
-    - name: Install Black
-      run: |
-        pip install black
-    - name: Run Black
-      run: |
-        black --check --diff .
+    - uses: pre-commit/action@v2.0.0
 
   test:
     name: "Build (${{ matrix.os }} Python ${{ matrix.python-version }})"
diff --git a/.gitignore b/.gitignore
index 566ae34..5c70e0c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -219,4 +219,7 @@ $RECYCLE.BIN/
 # Windows shortcuts
 *.lnk
 
+# VS Code config
+.vscode/
+
 # End of https://www.toptal.com/developers/gitignore/api/python,linux,windows,macos,visualstudiocode
\ No newline at end of file
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
new file mode 100644
index 0000000..84479e8
--- /dev/null
+++ b/.pre-commit-config.yaml
@@ -0,0 +1,22 @@
+# Install pre-commit hooks via
+# pre-commit install
+
+repos:
+
+  # - repo: git://github.com/pre-commit/pre-commit-hooks
+  #   rev: v2.2.3
+  #   hooks:
+  #   - id: check-json
+  #   - id: check-yaml
+  #   - id: end-of-file-fixer
+  #   - id: trailing-whitespace
+
+  # - repo: https://gitlab.com/pycqa/flake8
+  #   rev: 3.7.9
+  #   hooks:
+  #   - id: flake8
+
+  - repo: https://github.com/psf/black
+    rev: 20.8b1
+    hooks:
+    - id: black
diff --git a/sphinxext/rediraffe.py b/sphinxext/rediraffe.py
index 509aed2..3278f3e 100644
--- a/sphinxext/rediraffe.py
+++ b/sphinxext/rediraffe.py
@@ -117,6 +117,10 @@ def build_redirects(app: Sphinx, exception: Union[Exception, None]) -> None:
     """
     Build amd write redirects
     """
+    try:
+        app.env.redirected
+    except AttributeError:
+        app.env.redirected = {}
 
     if exception != None:
         return
@@ -208,6 +212,19 @@ def build_redirects(app: Sphinx, exception: Union[Exception, None]) -> None:
         build_redirect_from = Path(app.outdir) / redirect_from
         build_redirect_to = Path(app.outdir) / redirect_to
 
+        if (
+            build_redirect_from.exists()
+            and src_redirect_from.as_posix() in app.env.redirected
+        ):
+            # if it is still pointing to the same source, continue
+            if (
+                app.env.redirected[src_redirect_from.as_posix()]
+                == src_redirect_to.as_posix()
+            ):
+                continue
+            # otherwise remove and rewrite
+            build_redirect_from.unlink()
+
         if build_redirect_from.exists():
             logger.warning(
                 f'{yellow("(broken)")} {redirect_from} redirects to {redirect_to} but {build_redirect_from} already exists!'
@@ -240,6 +257,9 @@ def build_redirects(app: Sphinx, exception: Union[Exception, None]) -> None:
             logger.info(
                 f'{green("(good)")} {redirect_from} {green("-->")} {redirect_to}'
             )
+            app.env.redirected[
+                src_redirect_from.as_posix()
+            ] = src_redirect_to.as_posix()
 
 
 class CheckRedirectsDiffBuilder(Builder):
diff --git a/tests/test_ext.py b/tests/test_ext.py
index 23512f9..52293a0 100644
--- a/tests/test_ext.py
+++ b/tests/test_ext.py
@@ -5,6 +5,7 @@
 from sphinx.application import Sphinx
 from sphinx.errors import ExtensionError
 from pathlib import Path
+import shutil
 import logging
 
 from conftest import rel2url
@@ -27,6 +28,16 @@ def test_simple(self, app: Sphinx, ensure_redirect):
         assert app.statuscode == 0
         ensure_redirect("another.html", "index.html")
 
+    @pytest.mark.sphinx("html", testroot="simple")
+    def test_simple_rebuild(self, app: Sphinx, ensure_redirect):
+        if Path(app.outdir).exists():
+            shutil.rmtree(Path(app.outdir))
+        app.build()
+        assert app.statuscode == 0
+        app.build()
+        assert app.statuscode == 0
+        ensure_redirect("another.html", "index.html")
+
     @pytest.mark.sphinx("html", testroot="no_cycle")
     def test_no_cycle(self, app: Sphinx, ensure_redirect):
         app.build()
@@ -210,6 +221,16 @@ def test_simple(self, app: Sphinx, ensure_redirect):
         assert app.statuscode == 0
         ensure_redirect("another/index.html", "index.html")
 
+    @pytest.mark.sphinx("dirhtml", testroot="simple", freshenv=False)
+    def test_simple_rebuild(self, app: Sphinx, ensure_redirect):
+        if Path(app.outdir).exists():
+            shutil.rmtree(Path(app.outdir))
+        app.build()
+        assert app.statuscode == 0
+        app.build()
+        assert app.statuscode == 0
+        ensure_redirect("another/index.html", "index.html")
+
     @pytest.mark.sphinx("dirhtml", testroot="no_cycle")
     def test_no_cycle(self, app: Sphinx, ensure_redirect):
         app.build()
diff --git a/tox.ini b/tox.ini
new file mode 100644
index 0000000..512e8ed
--- /dev/null
+++ b/tox.ini
@@ -0,0 +1,19 @@
+# To use tox, see https://tox.readthedocs.io
+# Simply pip or conda install tox
+# If you use conda, you may also want to install tox-conda
+# then run `tox` or `tox -- {pytest args}`
+# To run in parallel using `tox -p` (this does not appear to work for this repo)
+
+# To rebuild the tox environment, for example when dependencies change, use
+# `tox -r`
+
+# Note: if the following error is encountered: `ImportError while loading conftest`
+# then then deleting compiled files has been found to fix it: `find . -name \*.pyc -delete`
+
+[tox]
+envlist = py{36,37,38}
+
+[testenv:py{36,37,38}]
+; recreate = false
+deps = -rtest-requirements.txt
+commands = pytest {posargs}