diff --git a/mlibc/include/stdlib.h b/mlibc/include/stdlib.h
index b2d181bb..afa54892 100644
--- a/mlibc/include/stdlib.h
+++ b/mlibc/include/stdlib.h
@@ -33,11 +33,12 @@
 typedef long size_t;
 #endif
 
-char* getenv (char const* s);
 int atoi (char const *s);
-void *malloc (size_t);
-void *realloc (void *p, size_t size);
 void exit (int);
+char* getenv (char const* s);
+void *malloc (size_t);
+unsigned long strtoul (char const *nptr, char **endptr, int base);
+void *realloc (void *p, size_t size);
 
 #endif // !(__GNUC__ && POSIX)
 
diff --git a/mlibc/libc-mes+tcc.c b/mlibc/libc-mes+tcc.c
index 3cdfaa5a..d9310d02 100644
--- a/mlibc/libc-mes+tcc.c
+++ b/mlibc/libc-mes+tcc.c
@@ -53,3 +53,9 @@ memcmp (void const *s1, void const *s2, size_t n)
 {
   return 0;
 }
+
+unsigned long
+strtoul (char const *nptr, char **endptr, int base)
+{
+  return 0;
+}