diff --git a/libc/include/android/fdsan.h b/libc/include/android/fdsan.h
index 59ce133..3de0649 100644
--- a/libc/include/android/fdsan.h
+++ b/libc/include/android/fdsan.h
@@ -159,7 +159,7 @@
  *
  * The return value points to memory with static lifetime, do not attempt to modify it.
  */
-const char* android_fdsan_get_tag_type(uint64_t tag) __INTRODUCED_IN(29);
+const char* _Nonnull android_fdsan_get_tag_type(uint64_t tag) __INTRODUCED_IN(29);
 
 /*
  * Get an owner tag's value, with the type masked off.