diff --git a/userland/nbpf/Makefile.in b/userland/nbpf/Makefile.in
index b0d8181..8221e41 100644
--- a/userland/nbpf/Makefile.in
+++ b/userland/nbpf/Makefile.in
@@ -1,4 +1,4 @@
-LEX = lex
+LEX = flex
 YACC = bison
 INCLUDE = -I../lib -I../../kernel
 LIBS=`../lib/pfring_config --libs` -lpthread #@NDPI_LIB@
