diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 2ed049d..ddcba0d 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -8,7 +8,6 @@ repos:
       types: [python]
       stages: [commit]
     - id: black
-      language_version: python3.6+
       name: black
       language: system
       entry: black
diff --git a/environment.yml b/environment.yml
index 0282a56..a7eb027 100644
--- a/environment.yml
+++ b/environment.yml
@@ -4,7 +4,7 @@ channels:
 dependencies:
 - python=3.7
 - requests
-- flask
+- flask<2.0.0,>=1.0.2
 - psutil
 - black
 - coverage
diff --git a/requirements.txt b/requirements.txt
index 08aae3b..90d07a1 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,5 +1,5 @@
 cellxgene>=0.15
-flask
+flask<2.0.0,>=1.0.2
 flask_api
 psutil
 requests