diff --git a/ddtrace/bootstrap/sitecustomize.py b/ddtrace/bootstrap/sitecustomize.py
index be7b7235a90..07f240768ed 100644
--- a/ddtrace/bootstrap/sitecustomize.py
+++ b/ddtrace/bootstrap/sitecustomize.py
@@ -98,7 +98,7 @@ def add_global_tags(tracer):
     if priority_sampling:
         opts["priority_sampling"] = asbool(priority_sampling)
 
-    opts["collect_metrics"] = asbool(get_env('runtime_metrics', 'enabled'))
+    opts['collect_metrics'] = asbool(get_env('runtime_metrics', 'enabled'))
 
     if opts:
         tracer.configure(**opts)