diff --git a/datadog_lambda/config.py b/datadog_lambda/config.py
index 9960953e..eeef642b 100644
--- a/datadog_lambda/config.py
+++ b/datadog_lambda/config.py
@@ -141,6 +141,9 @@ def _reset(self):
         "enabled" if config.fips_mode_enabled else "not enabled",
     )
 
+# disable css by default to prevent double counting in lambda
+if "DD_TRACE_COMPUTE_STATS" not in os.environ:
+    os.environ["DD_TRACE_COMPUTE_STATS"] = "false"
 
 if (
     "DD_INSTRUMENTATION_TELEMETRY_ENABLED" not in os.environ