diff --git a/src/ltlparse/ltlscan.ll b/src/ltlparse/ltlscan.ll
index 3d46450a7..7da6ec6d7 100644
--- a/src/ltlparse/ltlscan.ll
+++ b/src/ltlparse/ltlscan.ll
@@ -80,6 +80,8 @@ BOXDARROW {BOX}{DARROWL}|"|"{DARROWL}|"⤇"
       start_token = 0;
       if (t == token::START_LBT)
         BEGIN(lbt);
+      else
+        BEGIN(0);
       return t;
     }
   yylloc->step();