diff --git a/Makefile b/Makefile
index b49aebb..af467ef 100644
--- a/Makefile
+++ b/Makefile
@@ -17,7 +17,7 @@ CONFIG_LOCALVERSION =
 
 CPPFLAGS = -I libfdt
 WARNINGS = -Werror -Wall -Wpointer-arith -Wcast-qual -Wnested-externs \
-	-Wstrict-prototypes -Wmissing-prototypes
+	-Wstrict-prototypes -Wmissing-prototypes -Wredundant-decls
 CFLAGS = -g -Os -fPIC -Werror $(WARNINGS)
 
 BISON = bison
diff --git a/convert-dtsv0-lexer.l b/convert-dtsv0-lexer.l
index edb9110..89d540a 100644
--- a/convert-dtsv0-lexer.l
+++ b/convert-dtsv0-lexer.l
@@ -17,7 +17,7 @@
  *                                                                   USA
  */
 
-%option noyywrap nounput noinput
+%option noyywrap nounput noinput never-interactive
 
 %x INCLUDE
 %x BYTESTRING
diff --git a/dtc-lexer.l b/dtc-lexer.l
index 3c3434c..f8953f4 100644
--- a/dtc-lexer.l
+++ b/dtc-lexer.l
@@ -18,7 +18,7 @@
  *                                                                   USA
  */
 
-%option noyywrap nounput noinput
+%option noyywrap nounput noinput never-interactive
 
 %x INCLUDE
 %x BYTESTRING