diff --git a/Makefile b/Makefile
index d68f602..2ad028f 100644
--- a/Makefile
+++ b/Makefile
@@ -2,7 +2,7 @@ CC ?= gcc
 DEBUG ?= 0
 
 CFLAGS = -Wall -Werror -Wextra -Wpedantic -std=c99 -Ofast \
--D_POSIX_C_SOURCE=200809L
+-D_POSIX_C_SOURCE=200112L
 
 ifeq ($(DEBUG), 1)
 	CFLAGS += -g -DDEBUG
diff --git a/include/common.h b/include/common.h
index 065ab4b..9660199 100644
--- a/include/common.h
+++ b/include/common.h
@@ -6,6 +6,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <sys/types.h>
 
 /* enums */
 enum configurations_bitshift {
diff --git a/include/strdup.h b/include/strdup.h
new file mode 100644
index 0000000..09ee248
--- /dev/null
+++ b/include/strdup.h
@@ -0,0 +1,11 @@
+#ifndef _STRDUP_H
+#define _STRDUP_H
+
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+
+/* functions definitions */
+char* strdup(const char* s);
+
+#endif /* _STRDUP_H */
diff --git a/src/main.c b/src/main.c
index 1c98ab0..6d951f7 100644
--- a/src/main.c
+++ b/src/main.c
@@ -23,6 +23,7 @@
 #include "atoumax_base10.h"
 #include "corrupter.h"
 #include "file_type.h"
+#include "strdup.h"
 
 /* enums */
 enum arg_destinations {
diff --git a/src/strdup.c b/src/strdup.c
new file mode 100644
index 0000000..2c7ee5f
--- /dev/null
+++ b/src/strdup.c
@@ -0,0 +1,17 @@
+#include "strdup.h"
+
+/* function implementations */
+char* strdup(const char* s) {
+	if (s == NULL) {
+		errno = EINVAL;
+		return NULL;
+	}
+
+	char* copy = malloc((strlen(s) + 1) * sizeof(char));
+	if (copy == NULL)
+		return NULL;
+
+	strcpy(copy, s);
+
+	return copy;
+}