diff --git a/libc/include/sys/_system_properties.h b/libc/include/sys/_system_properties.h
index 89a1608..080280e 100644
--- a/libc/include/sys/_system_properties.h
+++ b/libc/include/sys/_system_properties.h
@@ -48,7 +48,6 @@
 
 #define PA_SIZE         (128 * 1024)
 
-#define SERIAL_VALUE_LEN(serial) ((serial) >> 24)
 #define SERIAL_DIRTY(serial) ((serial) & 1)
 
 __BEGIN_DECLS
@@ -61,6 +60,18 @@
 };
 
 #define PROP_MSG_SETPROP 1
+#define PROP_MSG_SETPROP2 0x00020001
+
+#define PROP_SUCCESS 0
+#define PROP_ERROR_READ_CMD 0x0004
+#define PROP_ERROR_READ_DATA 0x0008
+#define PROP_ERROR_READ_ONLY_PROPERTY 0x000B
+#define PROP_ERROR_INVALID_NAME 0x0010
+#define PROP_ERROR_INVALID_VALUE 0x0014
+#define PROP_ERROR_PERMISSION_DENIED 0x0018
+#define PROP_ERROR_INVALID_CMD 0x001B
+#define PROP_ERROR_HANDLE_CONTROL_MESSAGE 0x0020
+#define PROP_ERROR_SET_FAILED 0x0024
 
 /*
 ** Rules:
diff --git a/libc/include/sys/system_properties.h b/libc/include/sys/system_properties.h
index faed9a0..d80b2fe 100644
--- a/libc/include/sys/system_properties.h
+++ b/libc/include/sys/system_properties.h
@@ -30,6 +30,7 @@
 #define _INCLUDE_SYS_SYSTEM_PROPERTIES_H
 
 #include <sys/cdefs.h>
+#include <stddef.h>
 
 __BEGIN_DECLS
 
@@ -64,13 +65,17 @@
 /* Read the value of a system property.  Returns the length
 ** of the value.  Copies the value and \0 terminator into
 ** the provided value pointer.  Total length (including
-** terminator) will be no greater that PROP_VALUE_MAX.
+** terminator) will be no greater that PROP_VALUE_MAX for
+** __system_property_read.
 **
 ** If name is nonzero, up to PROP_NAME_MAX bytes will be
 ** copied into the provided name pointer.  The name will
 ** be \0 terminated.
 */
 int __system_property_read(const prop_info *pi, char *name, char *value);
+void __system_property_read_callback(const prop_info *pi,
+                                     void (*)(void* cookie, const char *name, const char *value),
+                                     void* cookie) __INTRODUCED_IN_FUTURE;
 
 /* Return a prop_info for the nth system property, or NULL if 
 ** there is no nth property.  Use __system_property_read() to