diff --git a/include/lib/libc/stdlib.h b/include/lib/libc/stdlib.h
index 24e7bae..b4a14e8 100644
--- a/include/lib/libc/stdlib.h
+++ b/include/lib/libc/stdlib.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2012-2017 Roberto E. Vargas Caballero
+ * Copyright (c) 2012-2021 Roberto E. Vargas Caballero
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -18,8 +18,12 @@
 
 #define _ATEXIT_MAX 1
 
+#define isspace(x)    (((x) == ' ') || ((x) == '\r') || ((x) == '\n') || \
+			((x) == '\t') || ((x) == '\b'))
+
 extern void abort(void);
 extern int atexit(void (*func)(void));
 extern void exit(int status);
 
+long strtol(const char *nptr, char **endptr, int base);
 #endif /* STDLIB_H */