diff --git a/libc/include/stdio.h b/libc/include/stdio.h
index 74208bc..cfcdf1a 100644
--- a/libc/include/stdio.h
+++ b/libc/include/stdio.h
@@ -210,7 +210,7 @@
 int vsscanf(const char* __restrict, const char* __restrict, __va_list) __scanflike(2, 0);
 
 #define L_ctermid 1024 /* size for ctermid() */
-char* ctermid(char*);
+char* ctermid(char*) __INTRODUCED_IN_FUTURE;
 
 FILE* fdopen(int, const char*);
 int fileno(FILE*);
diff --git a/libc/include/stdlib.h b/libc/include/stdlib.h
index 6fb2209..ffbce10 100644
--- a/libc/include/stdlib.h
+++ b/libc/include/stdlib.h
@@ -46,8 +46,8 @@
 extern __noreturn void _Exit(int) __INTRODUCED_IN(21);
 extern int atexit(void (*)(void));
 
-int at_quick_exit(void (*)(void));
-void quick_exit(int) __noreturn;
+int at_quick_exit(void (*)(void)) __INTRODUCED_IN(21);
+void quick_exit(int) __noreturn __INTRODUCED_IN(21);
 
 extern char* getenv(const char*);
 extern int putenv(char*);
diff --git a/libc/include/sys/time.h b/libc/include/sys/time.h
index f4ed321..ad5844a 100644
--- a/libc/include/sys/time.h
+++ b/libc/include/sys/time.h
@@ -47,12 +47,12 @@
 int utimes(const char*, const struct timeval*);
 
 #if defined(__USE_BSD)
-int futimes(int, const struct timeval[2]);
-int lutimes(const char*, const struct timeval[2]);
+int futimes(int, const struct timeval[2]) __INTRODUCED_IN_FUTURE;
+int lutimes(const char*, const struct timeval[2]) __INTRODUCED_IN_FUTURE;
 #endif
 
 #if defined(__USE_GNU)
-int futimesat(int, const char*, const struct timeval[2]);
+int futimesat(int, const char*, const struct timeval[2]) __INTRODUCED_IN_FUTURE;
 #endif
 
 #define timerclear(a)   \