2 files changed, 3 insertions, 2 deletions
diff --git a/Makefile b/Makefile
index a765ff0..b23c425 100644
--- a/Makefile
+++ b/Makefile
@@ -1,7 +1,7 @@
 PREFIX ?= /usr/local
 BINDIR ?= /bin
 
-CFLAGS = -Wunused-variable -Wunused-function
+CFLAGS ?= -std=c99 -Wunused-variable -Wunused-function
 
 all: vkill
 
diff --git a/vkill.c b/vkill.c
index 812f014..2f3f775 100644
--- a/vkill.c
+++ b/vkill.c
@@ -1,10 +1,11 @@
+#define _POSIX_C_SOURCE 2008
+
 #include <linux/limits.h>
 #include <strings.h>
 #include <unistd.h>
 #include <termios.h>
 #include <dirent.h>
 #include <wait.h>
-#include <ctype.h>
 #include <signal.h>
 #include <err.h>
 #include <string.h>