diff --git a/build.yaml b/build.yaml
index 5517f5b..0def606 100644
--- a/build.yaml
+++ b/build.yaml
@@ -9,7 +9,7 @@ targets:
           # List any dart2js specific args here, or omit it.
           dart2js_args:
             # Omit type checks TODO change to -O4 at some point (e.g., --trust-primitives)
-            - -O3
+            - -O2
             # Generate CSP-compliant code since it will be used most often in prod
             - --csp
             # Disable minification for dart2js tests