diff --git a/canaille/oidc/endpoints/oauth.py b/canaille/oidc/endpoints/oauth.py
index f87616f1..94e1a4da 100644
--- a/canaille/oidc/endpoints/oauth.py
+++ b/canaille/oidc/endpoints/oauth.py
@@ -15,6 +15,7 @@ from flask import request
 from flask import session
 from flask import url_for
 from werkzeug.datastructures import CombinedMultiDict
+from werkzeug.exceptions import HTTPException
 
 from canaille import csrf
 from canaille.app import models
@@ -42,6 +43,14 @@ from .well_known import openid_configuration
 bp = Blueprint("endpoints", __name__, url_prefix="/oauth")
 
 
+@bp.errorhandler(HTTPException)
+def http_error_handler(error):
+    return {
+        "error": error.name.lower().replace(" ", "_"),
+        "error_description": error.description,
+    }, error.code
+
+
 @bp.route("/authorize", methods=["GET", "POST"])
 def authorize():
     current_app.logger.debug(
diff --git a/tests/oidc/test_errors.py b/tests/oidc/test_errors.py
new file mode 100644
index 00000000..aa86d9a0
--- /dev/null
+++ b/tests/oidc/test_errors.py
@@ -0,0 +1,7 @@
+def test_json_oauth_errors(testclient):
+    """Checks that HTTP errors on the oauth endpoints are in the JSON format."""
+    res = testclient.get("/oauth/invalid", status=404)
+    assert res.json == {
+        "error": "not_found",
+        "error_description": "The requested URL was not found on the server. If you entered the URL manually please check your spelling and try again.",
+    }