diff --git a/libc/include/execinfo.h b/libc/include/execinfo.h
index 347ae92..88f4ae7 100644
--- a/libc/include/execinfo.h
+++ b/libc/include/execinfo.h
@@ -47,7 +47,7 @@
  *
  * Available since API level 33.
  */
-int backtrace(void** buffer, int size) __INTRODUCED_IN(33);
+int backtrace(void* _Nonnull * _Nonnull buffer, int size) __INTRODUCED_IN(33);
 
 /**
  * [backtrace_symbols(3)](https://man7.org/linux/man-pages/man3/backtrace_symbols.3.html)
@@ -59,7 +59,7 @@
  *
  * Available since API level 33.
  */
-char** backtrace_symbols(void* const* buffer, int size) __INTRODUCED_IN(33);
+char* _Nullable * _Nullable backtrace_symbols(void* _Nonnull const* _Nonnull buffer, int size) __INTRODUCED_IN(33);
 
 /**
  * [backtrace_symbols_fd(3)](https://man7.org/linux/man-pages/man3/backtrace_symbols_fd.3.html)
@@ -69,6 +69,6 @@
  *
  * Available since API level 33.
  */
-void backtrace_symbols_fd(void* const* buffer, int size, int fd) __INTRODUCED_IN(33);
+void backtrace_symbols_fd(void* _Nonnull const* _Nonnull buffer, int size, int fd) __INTRODUCED_IN(33);
 
 __END_DECLS