diff --git a/news/2 Fixes/1535.md b/news/2 Fixes/1535.md
new file mode 100644
index 000000000000..04b3bc69c3dd
--- /dev/null
+++ b/news/2 Fixes/1535.md	
@@ -0,0 +1 @@
+Ensure Flask application is launched with multi-threading disabled, when run in the CI tests.
diff --git a/src/test/debugger/web.framework.test.ts b/src/test/debugger/web.framework.test.ts
index 0036fe9041f3..9b23a691f83c 100644
--- a/src/test/debugger/web.framework.test.ts
+++ b/src/test/debugger/web.framework.test.ts
@@ -69,6 +69,7 @@ suite(`Django and Flask Debugging: ${debuggerType}`, () => {
             'run',
             '--no-debugger',
             '--no-reload',
+            '--without-threads',
             '--port',
             `${port}`
         ];