diff --git a/src/A3t.cpp b/src/A3t.cpp
index 0fce55e8e..d8806b93c 100644
--- a/src/A3t.cpp
+++ b/src/A3t.cpp
@@ -547,6 +547,9 @@ const std::string A3t::getFilterExpression ()
     }
   }
 
+  if (sequence != "")
+    sequence = "( " + sequence + " )";
+
   return sequence;