diff --git a/lib/datadog/tracing/trace_operation.rb b/lib/datadog/tracing/trace_operation.rb
index 3b209c01af..11450097cf 100644
--- a/lib/datadog/tracing/trace_operation.rb
+++ b/lib/datadog/tracing/trace_operation.rb
@@ -167,7 +167,7 @@ def get_tag(key)
       end
 
       def get_metric(key)
-        @metric[key?] || (root_span && root_span.get_metric(key))
+        super || (root_span && root_span.get_metric(key))
       end
 
       def tags