diff --git a/coolamqp/attaches/declarer.py b/coolamqp/attaches/declarer.py
index ebc579d44583f6cd5fe8d8422ec7e3c8bbd75ed6..7eecc8e2f2748db76aece9ef28e59d41a13d0215 100644
--- a/coolamqp/attaches/declarer.py
+++ b/coolamqp/attaches/declarer.py
@@ -85,7 +85,7 @@ class Operation(object):
             self.enqueued_span = None
 
     def span_finished(self):
-        if self.processing_span is None:
+        if self.processing_span is not None:
             self.processing_span.finish()
             self.processing_span = None