diff --git a/reading_machine/src/Action.cpp b/reading_machine/src/Action.cpp
index ca954735fd571324a78a3d91c38a22a7b9c781c4..997f251be36caca67e35b46e63c59570460a8e41 100644
--- a/reading_machine/src/Action.cpp
+++ b/reading_machine/src/Action.cpp
@@ -92,7 +92,7 @@ Action Action::addToHypothesis(const std::string & colName, std::size_t lineInde
   auto apply = [colName, lineIndex, addition](Config & config, Action &)
   {
     auto & current = config.getLastNotEmptyHyp(colName, lineIndex);
-    current = util::isEmpty(current) ? addition : '|' + addition;
+    current = util::isEmpty(current) ? addition : current.get() + '|' + addition;
   };
 
   auto undo = [colName, lineIndex](Config & config, Action &)