diff --git a/src/backend/replication/Makefile b/src/backend/replication/Makefile
index da8bcf0..2e32788 100644
--- a/src/backend/replication/Makefile
+++ b/src/backend/replication/Makefile
@@ -23,6 +23,7 @@ include $(top_srcdir)/src/backend/common.mk
 
 # repl_scanner is compiled as part of repl_gram
 repl_gram.o: repl_scanner.c
+repl_scanner.c: FLEXFLAGS = -CF -p -i
 
 # syncrep_scanner is complied as part of syncrep_gram
 syncrep_gram.o: syncrep_scanner.c