diff --git a/etc/ci/buildbot_steps.yml b/etc/ci/buildbot_steps.yml
index cb2bbf1ab99..ae3f2afd9fb 100644
--- a/etc/ci/buildbot_steps.yml
+++ b/etc/ci/buildbot_steps.yml
@@ -3,7 +3,7 @@ env:
   CARGO_INCREMENTAL: "0"
   CCACHE: sccache
   RUSTC_WRAPPER: sccache
-  SCCACHE_IDLE_TIMEOUT: 600
+  SCCACHE_IDLE_TIMEOUT: "600"
 
 mac-rel-wpt1:
   - ./mach clean-nightlies --keep 3 --force