diff --git a/src/tgbaalgos/ltl2tgba_fm.cc b/src/tgbaalgos/ltl2tgba_fm.cc
index 59c72052c..b732d0e58 100644
--- a/src/tgbaalgos/ltl2tgba_fm.cc
+++ b/src/tgbaalgos/ltl2tgba_fm.cc
@@ -807,7 +807,7 @@ namespace spot
 		      res_ |= label & tail_bdd;
 		    }
 
-		  if (dynamic_cast<constant*>(dest) == 0)
+		  if (dest->kind() != formula::Constant)
 		    {
 		      // If the destination is not a constant, it
 		      // means it can have successors.  Fusion the