diff --git a/src/ltlparse/ltlscan.ll b/src/ltlparse/ltlscan.ll
index 6624af883..b7c6291d4 100644
--- a/src/ltlparse/ltlscan.ll
+++ b/src/ltlparse/ltlscan.ll
@@ -24,6 +24,7 @@
 %option prefix="ltlyy"
 %option outfile="lex.yy.c"
 %option stack
+%option never-interactive
 
 %{
 #include <cstdlib>