diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 5478126..bad1152 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -1,15 +1,13 @@
 name: CI
 
-on:
-  - push
-  - pull_request
+on: [push, pull_request]
 
 jobs:
   CI:
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-20.04
     steps:
       - name: 'Check out code'
-        uses: actions/checkout@v4
+        uses: actions/checkout@v3
 
       - name: 'Install dependencies'
         run: |
@@ -30,7 +28,7 @@ jobs:
           make -C build
 
       - name: 'Upload binary'
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v3
         with:
           name: pico-uart-bridge.uf2
           path: build/uart_bridge.uf2
diff --git a/pico-sdk b/pico-sdk
index 6a7db34..2e6142b 160000
--- a/pico-sdk
+++ b/pico-sdk
@@ -1 +1 @@
-Subproject commit 6a7db34ff63345a7badec79ebea3aaef1712f374
+Subproject commit 2e6142b15b8a75c1227dd3edbe839193b2bf9041
diff --git a/uart-bridge.c b/uart-bridge.c
index c4e0805..9791df6 100644
--- a/uart-bridge.c
+++ b/uart-bridge.c
@@ -301,6 +301,8 @@ int main(void)
 {
 	int itf;
 
+	set_sys_clock_khz(250000, false);
+
 	usbd_serial_init();
 
 	for (itf = 0; itf < CFG_TUD_CDC; itf++)