diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 60cd30e..1dd8e0c 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -12,9 +12,9 @@ jobs:
         os: [ ubuntu-latest, windows-latest, macos-latest ]
         # The versions should contain (at least) the lowest requirement
         #    and a version that is more up to date.
-        toit-version: [ v2.0.0-alpha.170, latest ]
+        toit-version: [ v2.0.0-alpha.190, latest ]
         include:
-          - toit-version: v2.0.0-alpha.170
+          - toit-version: v2.0.0-alpha.190
             version-name: old
           - toit-version: latest
             version-name: new
diff --git a/package.yaml b/package.yaml
index 9246a55..451e1af 100644
--- a/package.yaml
+++ b/package.yaml
@@ -1,4 +1,4 @@
 name: http
 description: An HTTP server and client.
 environment:
-  sdk: ^2.0.0-alpha.170
+  sdk: ^2.0.0-alpha.189.1
diff --git a/src/chunked.toit b/src/chunked.toit
index eb4f275..5532a9c 100644
--- a/src/chunked.toit
+++ b/src/chunked.toit
@@ -117,6 +117,5 @@ class ChunkedWriter_ extends io.CloseableWriter:
     connection_ = null
 
   write-header_ length/int:
-    writer_.write
-      length.stringify 16
+    writer_.write (length.to-string --radix=16)
     writer_.write CRLF_