diff --git a/libc/include/android/dlext.h b/libc/include/android/dlext.h
index d0200c4..431e5ce 100644
--- a/libc/include/android/dlext.h
+++ b/libc/include/android/dlext.h
@@ -178,6 +178,8 @@
  * Opens the given library. The `__filename` and `__flags` arguments are
  * the same as for [dlopen(3)](http://man7.org/linux/man-pages/man3/dlopen.3.html),
  * with the Android-specific flags supplied via the `flags` member of `__info`.
+ *
+ * Available since API level 21.
  */
 void* android_dlopen_ext(const char* __filename, int __flags, const android_dlextinfo* __info)
   __INTRODUCED_IN(21);