diff --git a/conf/common.rmk b/conf/common.rmk
index 87ae1e202..a83d10662 100644
--- a/conf/common.rmk
+++ b/conf/common.rmk
@@ -653,7 +653,7 @@ normal_mod_LDFLAGS = $(COMMON_LDFLAGS)
 # For sh.mod.
 sh_mod_SOURCES = script/main.c script/script.c script/execute.c \
 	script/function.c script/lexer.c grub_script.tab.c grub_script.yy.c
-sh_mod_CFLAGS = $(COMMON_CFLAGS) $(POSIX_CFLAGS)
+sh_mod_CFLAGS = $(COMMON_CFLAGS) $(POSIX_CFLAGS) -Wno-error
 sh_mod_LDFLAGS = $(COMMON_LDFLAGS)
 
 ifneq (, $(FONT_SOURCE))
diff --git a/configure.ac b/configure.ac
index 1f55a9ca7..0af597bd3 100644
--- a/configure.ac
+++ b/configure.ac
@@ -192,7 +192,7 @@ AC_PROG_MKDIR_P
 if test "x$LEX" = x; then
   AC_MSG_ERROR([flex is not found])
 else
-  version=`$LEX --version 2>/dev/null | $SED -e 's/flex //' | $AWK 'BEGIN { FS = "."; } { printf "%d", $1 * 10000 + $2 * 100 + $3;}'`
+  version=`$LEX --version 2>/dev/null | $SED -e 's/flex//' -e 's/version//' | $AWK -F "." '{ printf "%d", $1 * 10000 + $2 * 100 + $3;}'`
   if test -n "$version" -a "$version" -ge 20535; then
     :
   else
diff --git a/script/yylex.l b/script/yylex.l
index 4d7c66448..0cf33c951 100644
--- a/script/yylex.l
+++ b/script/yylex.l
@@ -86,12 +86,6 @@ typedef size_t yy_size_t;
 #define exit(...)
 #endif
 
-#pragma GCC diagnostic warning "-Wunused-variable"
-#pragma GCC diagnostic warning "-Wunused-function"
-#pragma GCC diagnostic warning "-Wunused-parameter"
-#pragma GCC diagnostic warning "-Wstrict-prototypes"
-#pragma GCC diagnostic warning "-Wmissing-prototypes"
-
 }
 
 %option ecs