diff --git a/libc/include/sys/system_properties.h b/libc/include/sys/system_properties.h
index e8b6e34..1303079 100644
--- a/libc/include/sys/system_properties.h
+++ b/libc/include/sys/system_properties.h
@@ -71,9 +71,13 @@
  *
  * Available since API level 26.
  */
+
+#if __BIONIC_AVAILABILITY_GUARD(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);
+#endif /* __BIONIC_AVAILABILITY_GUARD(26) */
+
 
 /**
  * Passes a `prop_info` for each system property to the provided
@@ -101,8 +105,12 @@
  * Available since API level 26.
  */
 struct timespec;
+
+#if __BIONIC_AVAILABILITY_GUARD(26)
 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);
+#endif /* __BIONIC_AVAILABILITY_GUARD(26) */
+
 
 /**
  * Deprecated: there's no limit on the length of a property name since
@@ -233,7 +241,11 @@
  *
  * Available since API level 35.
  */
+
+#if __BIONIC_AVAILABILITY_GUARD(35)
 int __system_properties_zygote_reload(void) __INTRODUCED_IN(35);
+#endif /* __BIONIC_AVAILABILITY_GUARD(35) */
+
 
 /**
  * Deprecated: previously for testing, but now that SystemProperties is its own