diff --git a/include/lib/libc/stdlib.h b/include/lib/libc/stdlib.h
index a0354fa..4641e56 100644
--- a/include/lib/libc/stdlib.h
+++ b/include/lib/libc/stdlib.h
@@ -28,4 +28,5 @@
 long strtol(const char *nptr, char **endptr, int base);
 unsigned long strtoul(const char *nptr, char **endptr, int base);
 long long strtoll(const char *nptr, char **endptr, int base);
+unsigned long long strtoull(const char *nptr, char **endptr, int base);
 #endif /* STDLIB_H */