diff --git a/libc/include/sys/system_properties.h b/libc/include/sys/system_properties.h
index 99a6e59..d3e0d8d 100644
--- a/libc/include/sys/system_properties.h
+++ b/libc/include/sys/system_properties.h
@@ -48,7 +48,7 @@
 
 /* Set a system property by name.
 **/
-int __system_property_set(const char* key, const char* value) __INTRODUCED_IN(21);
+int __system_property_set(const char* key, const char* value) __INTRODUCED_IN(12);
 
 /* Return a pointer to the system property named name, if it
 ** exists, or NULL if there is no such property.  Use 
@@ -94,7 +94,7 @@
 ** not a bug.
 */
 int __system_property_foreach(void (*propfn)(const prop_info* pi, void* cookie), void* cookie)
-  __INTRODUCED_IN(21);
+  __INTRODUCED_IN(19);
 
 __END_DECLS