diff --git a/site/app.yaml b/site/app.yaml
index dea2b0d..ad8626e 100644
--- a/site/app.yaml
+++ b/site/app.yaml
@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-runtime: go115
+runtime: go121
 
 default_expiration: "1m"