diff --git a/libc/include/sys/system_properties.h b/libc/include/sys/system_properties.h
index a2e1923..06b2188 100644
--- a/libc/include/sys/system_properties.h
+++ b/libc/include/sys/system_properties.h
@@ -43,7 +43,7 @@
 /*
  * Sets system property `name` to `value`, creating the system property if it doesn't already exist.
  */
-int __system_property_set(const char* __name, const char* __value);
+int __system_property_set(const char* _Nonnull __name, const char* _Nonnull __value);
 
 /*
  * Returns a `prop_info` corresponding system property `name`, or nullptr if it doesn't exist.
@@ -51,14 +51,14 @@
  *
  * Property lookup is expensive, so it can be useful to cache the result of this function.
  */
-const prop_info* __system_property_find(const char* __name);
+const prop_info* _Nullable __system_property_find(const char* _Nonnull __name);
 
 /*
  * Calls `callback` with a consistent trio of name, value, and serial number for property `pi`.
  */
-void __system_property_read_callback(const prop_info* __pi,
-    void (*__callback)(void* __cookie, const char* __name, const char* __value, uint32_t __serial),
-    void* __cookie) __INTRODUCED_IN(26);
+void __system_property_read_callback(const prop_info* _Nonnull __pi,
+    void (* _Nonnull __callback)(void* _Nullable __cookie, const char* _Nonnull __name, const char* _Nonnull __value, uint32_t __serial),
+    void* _Nullable __cookie) __INTRODUCED_IN(26);
 
 /*
  * Passes a `prop_info` for each system property to the provided
@@ -66,13 +66,13 @@
  *
  * This method is for inspecting and debugging the property system, and not generally useful.
  */
-int __system_property_foreach(void (*__callback)(const prop_info* __pi, void* __cookie), void* __cookie)
+int __system_property_foreach(void (* _Nonnull __callback)(const prop_info* _Nonnull __pi, void* _Nullable __cookie), void* _Nullable __cookie)
   __INTRODUCED_IN(19);
 
 /*
  * Waits for the specific system property identified by `pi` to be updated
  * past `old_serial`. Waits no longer than `relative_timeout`, or forever
- * if `relaive_timeout` is null.
+ * if `relative_timeout` is null.
  *
  * If `pi` is null, waits for the global serial number instead.
  *
@@ -82,17 +82,17 @@
  * timed out.
  */
 struct timespec;
-bool __system_property_wait(const prop_info* __pi, uint32_t __old_serial, uint32_t* __new_serial_ptr, const struct timespec* __relative_timeout)
+bool __system_property_wait(const prop_info* _Nullable __pi, uint32_t __old_serial, uint32_t* _Nonnull __new_serial_ptr, const struct timespec* _Nullable __relative_timeout)
     __INTRODUCED_IN(26);
 
 /* Deprecated. In Android O and above, there's no limit on property name length. */
 #define PROP_NAME_MAX   32
 /* Deprecated. Use __system_property_read_callback instead. */
-int __system_property_read(const prop_info* __pi, char* __name, char* __value);
+int __system_property_read(const prop_info* _Nonnull __pi, char* _Nullable __name, char* _Nonnull __value);
 /* Deprecated. Use __system_property_read_callback instead. */
-int __system_property_get(const char* __name, char* __value);
+int __system_property_get(const char* _Nonnull __name, char* _Nonnull __value);
 /* Deprecated. Use __system_property_foreach instead. */
-const prop_info* __system_property_find_nth(unsigned __n);
+const prop_info* _Nullable __system_property_find_nth(unsigned __n);
 
 __END_DECLS