diff --git a/sys/include/ape/stdlib.h b/sys/include/ape/stdlib.h
index 896439723..4f531a232 100644
--- a/sys/include/ape/stdlib.h
+++ b/sys/include/ape/stdlib.h
@@ -49,6 +49,10 @@ extern int wctomb(char *, wchar_t);
 extern size_t mbstowcs(wchar_t *, const char *, size_t);
 extern size_t wcstombs(char *, const wchar_t *, size_t);
 
+#ifdef _BSD_SOURCE
+extern char *mktemp(char *);
+#endif
+
 #ifdef _POSIX_C_SOURCE
 extern int mkstemp(char *template);
 #endif