diff --git a/tests/requirements.txt b/tests/requirements.txt
index ed7c5227..07c4a577 100644
--- a/tests/requirements.txt
+++ b/tests/requirements.txt
@@ -15,5 +15,8 @@ psutil
 ## Used in Python code that is run/debugged by the tests:
 
 django
-flask
 requests
+
+# https://github.com/microsoft/ptvsd/issues/1574
+# Remove specific version once Flask 1.1.2 is released.
+flask==1.0.3