diff --git a/pyproject.toml b/pyproject.toml
index 2b3c8f4d..fea32205 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -53,7 +53,7 @@ complete = [
     "boto3>=1.14.44",
     "dask",
     "distributed",
-    "Flask<3.0.0",
+    "Flask<4.0.0",
     "Flask-RangeRequest",
     "fsspec[http,s3]>=2023.12.0",
     "lxml",
@@ -85,7 +85,7 @@ s3 = [
     "s3fs!=2023.9.0",
 ]
 serve = [
-    "Flask<3.0.0",
+    "Flask<4.0.0",
     "Flask-RangeRequest",
     "werkzeug>=0.15",
 ]
diff --git a/requirements.txt b/requirements.txt
index 745b4721..d6d87307 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -9,7 +9,7 @@ dask
 distributed
 fiona>=1.8.13.post1
 flask-rangerequest
-flask<3.0.0
+flask<4.0.0
 fsspec
 fsspec[http,s3]>=2023.12.0
 fsspec[http]