diff --git a/core/libs/prx/libSceSystemService/Export.cpp b/core/libs/prx/libSceSystemService/Export.cpp
index da7831be4..fc2b46ac9 100644
--- a/core/libs/prx/libSceSystemService/Export.cpp
+++ b/core/libs/prx/libSceSystemService/Export.cpp
@@ -92,7 +92,8 @@ int APS5_VABI sceSystemServiceParamGetInt(int paramId, int* value) {
   return SYSTEM_SERVICE_ERROR_PARAMETER;
  }
  switch (paramId) {
-  case SYSTEM_SERVICE_PARAM_ID_LANG: *value = ConsoleLanguage(); break;
+  case SYSTEM_SERVICE_PARAM_ID_LANG:
+  case SYSTEM_SERVICE_PARAM_ID_400: *value = ConsoleLanguage(); break;
   case SYSTEM_SERVICE_PARAM_ID_DATE_FORMAT: *value = SYSTEM_SERVICE_PARAM_DATE_FORMAT_DDMMYYYY; break;
   case SYSTEM_SERVICE_PARAM_ID_TIME_FORMAT: *value = SYSTEM_SERVICE_PARAM_TIME_FORMAT_24HOUR; break;
   case SYSTEM_SERVICE_PARAM_ID_TIME_ZONE: *value = 0; break;
diff --git a/core/libs/prx/libSceSystemService/SystemService.hpp b/core/libs/prx/libSceSystemService/SystemService.hpp
index 01f6f34f2..99b73cc0b 100644
--- a/core/libs/prx/libSceSystemService/SystemService.hpp
+++ b/core/libs/prx/libSceSystemService/SystemService.hpp
@@ -17,6 +17,7 @@ constexpr int SYSTEM_SERVICE_PARAM_ID_TIME_ZONE = 4;
 constexpr int SYSTEM_SERVICE_PARAM_ID_SUMMERTIME = 5;
 constexpr int SYSTEM_SERVICE_PARAM_ID_SYSTEM_NAME = 6;
 constexpr int SYSTEM_SERVICE_PARAM_ID_GAME_PARENTAL_LEVEL = 7;
+constexpr int SYSTEM_SERVICE_PARAM_ID_400 = 400;
 constexpr int SYSTEM_SERVICE_PARAM_ID_ENTER_BUTTON_ASSIGN = 1000;
 
 constexpr std::size_t SYSTEM_SERVICE_MAX_SYSTEM_NAME_LENGTH = 65;
diff --git a/core/libs/tests/GuestSystemServiceLanguage.cpp b/core/libs/tests/GuestSystemServiceLanguage.cpp
index 4b0e67f4d..efd37f499 100644
--- a/core/libs/tests/GuestSystemServiceLanguage.cpp
+++ b/core/libs/tests/GuestSystemServiceLanguage.cpp
@@ -21,20 +21,27 @@ void SetLanguage(const char* value) {
 int Language() {
     int value = -1;
     Require(sceSystemServiceParamGetInt(SYSTEM_SERVICE_PARAM_ID_LANG, &value) == SYSTEM_SERVICE_OK);
+    int sameValue = -1;
+    Require(sceSystemServiceParamGetInt(SYSTEM_SERVICE_PARAM_ID_400, &sameValue) == SYSTEM_SERVICE_OK);
+    Require(sameValue == value);
     return value;
 }
 
-bool Rejected(const char* value) {
-    SetLanguage(value);
+bool ParameterRejected(int paramId) {
     int language = -1;
     try {
-        static_cast<void>(sceSystemServiceParamGetInt(SYSTEM_SERVICE_PARAM_ID_LANG, &language));
+        static_cast<void>(sceSystemServiceParamGetInt(paramId, &language));
     } catch (const std::runtime_error& error) {
         return language == -1 && std::string(error.what()).find("ANYPS5_LANGUAGE") != std::string::npos;
     }
     return false;
 }
 
+bool Rejected(const char* value) {
+    SetLanguage(value);
+    return ParameterRejected(SYSTEM_SERVICE_PARAM_ID_LANG) && ParameterRejected(SYSTEM_SERVICE_PARAM_ID_400);
+}
+
 }
 
 int main() {
@@ -54,6 +61,7 @@ int main() {
 
     SetLanguage("arabic");
     Require(sceSystemServiceParamGetInt(SYSTEM_SERVICE_PARAM_ID_LANG, nullptr) == SYSTEM_SERVICE_ERROR_PARAMETER);
+    Require(sceSystemServiceParamGetInt(SYSTEM_SERVICE_PARAM_ID_400, nullptr) == SYSTEM_SERVICE_ERROR_PARAMETER);
     int enterButton = -1;
     Require(sceSystemServiceParamGetInt(SYSTEM_SERVICE_PARAM_ID_ENTER_BUTTON_ASSIGN, &enterButton) == SYSTEM_SERVICE_OK);
     Require(enterButton == SYSTEM_SERVICE_PARAM_ENTER_BUTTON_CROSS);
diff --git a/docs/dev/TechnicalDebt.md b/docs/dev/TechnicalDebt.md
index 0fa78fec4..8be9a265a 100644
--- a/docs/dev/TechnicalDebt.md
+++ b/docs/dev/TechnicalDebt.md
@@ -296,7 +296,7 @@ Throughout the project, every function at every stage either **does exactly what
 - [sceUserServiceGetAgeLevel](../../core/libs/prx/libSceUserService/Export.cpp) (libSceUserService) - the meaning of the value is unknown; 0 is reported, as for the unset game presets. PPSA12544 (Unity) only stores it for its user profile
 - [sceGameUpdateGetAddcontLatestVersion](../../core/libs/prx/libSceGameUpdate/Export.cpp) (libSceGameUpdate) - a null `entitlement_label` throws: KytyPS5 accepts it, prosper returns `0x80412803`. Bytes after `found` are zeroed as in KytyPS5; prosper leaves them untouched
 - [sceSystemServiceParamGetString](../../core/libs/prx/libSceSystemService/Export.cpp) (libSceSystemService) - the system name (parameter 6) is the fixed `PS5`, not the console's name; other parameters and buffers of 1 to 64 bytes throw
-- [sceSystemServiceParamGetInt](../../core/libs/prx/libSceSystemService/Export.cpp) (libSceSystemService) - console language numbers 0 to 29 follow the PS4 SDK enum in [OpenOrbis](https://github.com/OpenOrbis/OpenOrbis-PS4-Toolchain/blob/06fcf7fd108fa080035cdd3259ed22eb07e0508c/include/orbis/_types/sys_service.h#L54-L83) (21 Arabic). 30 (Ukrainian) is not in it and follows PPSA99505 ([Jelly5](https://github.com/02dnot/Jelly5/blob/552b866d89b2a58b27f7f7b0484dc743ce235526/app/src/app/i18n.cpp#L29-L60)) and PPSA99002 ([ProsperoLight](https://github.com/blackbearreloaded/ProsperoLight/blob/b708bbde3457bef1073a9ab6959957cb691e8e2f/include/i18n.hpp#L252-L309)), whose numbers agree with the enum. Not confirmed on a console, and neither title starts on `main` yet. Without `ANYPS5_LANGUAGE` the language is English (United States); the date format, time format, time zone, summer time and enter button stay fixed
+- [sceSystemServiceParamGetInt](../../core/libs/prx/libSceSystemService/Export.cpp) (libSceSystemService) - console language numbers 0 to 29 follow the PS4 SDK enum in [OpenOrbis](https://github.com/OpenOrbis/OpenOrbis-PS4-Toolchain/blob/06fcf7fd108fa080035cdd3259ed22eb07e0508c/include/orbis/_types/sys_service.h#L54-L83) (21 Arabic). 30 (Ukrainian) is not in it and follows PPSA99505 ([Jelly5](https://github.com/02dnot/Jelly5/blob/552b866d89b2a58b27f7f7b0484dc743ce235526/app/src/app/i18n.cpp#L29-L60)) and PPSA99002 ([ProsperoLight](https://github.com/blackbearreloaded/ProsperoLight/blob/b708bbde3457bef1073a9ab6959957cb691e8e2f/include/i18n.hpp#L252-L309)), whose numbers agree with the enum. Not confirmed on a console, and neither title starts on `main` yet. Parameter 400 returns the same number as parameter 1: PPSA01325 asks for 400 first, asks for 1 when that fails, and uses either answer as an index into the same 31 languages; in the PS5 10.01 and 12.60 `libSceSystemService` modules parameter 400 reads the same registry value as parameter 1, without parameter 1's mapping of newer language numbers by SDK version, and returns 0x80a10003 when an imported check that is not identified returns 1; the 4.03 module has no parameter 400. Neither the mapping nor that error is modelled, and the parameter's name is not known. Without `ANYPS5_LANGUAGE` the language is English (United States); the date format, time format, time zone, summer time and enter button stay fixed
 - [sceNgs2ReportRegisterHandler, sceNgs2ReportUnregisterHandler](../../core/libs/prx/libSceNgs2.native/src/Unimplemented.cpp) (libSceNgs2.native, NIDs `uBIN24Tv2MI`, `nPzb7Ly-VjE`) are throwing stubs. The signatures (report type, handler, user data, out handle) and (report handle) follow [SharpProspero](https://github.com/SvenGDK/SharpProspero) and [shadPS4](https://github.com/shadps4-emu/shadPS4)'s `ngs2_report.h`. No report is produced yet, so registering a handler cannot be honoured. PPSA04540 imports both and registers a CPU load handler (type 5)
 - [sceNgs2SystemSetSampleRate, sceNgs2SystemSetUserData, sceNgs2SystemGetUserData, sceNgs2SystemLock, sceNgs2SystemUnlock](../../core/libs/prx/libSceNgs2.native/src/System.cpp) (libSceNgs2.native) - shadPS4 only checks the system handle (`INVALID_SYSTEM_HANDLE`) and SharpProspero names what each call does; neither gives the other limits. A sample rate of 0 and a null user data pointer throw, any other rate is accepted, and changing the rate while a sampler filter is enabled throws because the filter coefficients were computed for the old rate. Lock and unlock take the same lock as `sceNgs2RackLock`
 - [sceNgs2RackGetInfo](../../core/libs/prx/libSceNgs2.native/src/Rack.cpp) (libSceNgs2.native) - field order from [shadPS4](https://github.com/shadps4-emu/shadPS4)'s `OrbisNgs2RackInfo` with the 64-byte name of the other info structures (216 bytes); `type` is assumed to be the rack id divided by 0x1000, `min_grain_samples` 64 (the system minimum) and `state_flags` 1; `uid` comes from a per-process rack counter, `render_count` is the owning system's render count and `active_voice_count` counts voices that are not empty (paused and stopped voices included). The last process ratio and tick and `active_channel_work_count` are left zero