diff --git a/libraries/libstratosphere/include/stratosphere/pgl/sf/pgl_sf_i_shell_interface.hpp b/libraries/libstratosphere/include/stratosphere/pgl/sf/pgl_sf_i_shell_interface.hpp
index 9046b2ef2..e4339411c 100644
--- a/libraries/libstratosphere/include/stratosphere/pgl/sf/pgl_sf_i_shell_interface.hpp
+++ b/libraries/libstratosphere/include/stratosphere/pgl/sf/pgl_sf_i_shell_interface.hpp
@@ -35,7 +35,8 @@ namespace ams::pgl::sf {
         AMS_SF_METHOD_INFO(C, H,  9, Result, IsApplicationCrashReportEnabled,       (ams::sf::Out<bool> out))                                                                       \
         AMS_SF_METHOD_INFO(C, H, 10, Result, EnableApplicationAllThreadDumpOnCrash, (bool enabled))                                                                                 \
         AMS_SF_METHOD_INFO(C, H, 12, Result, TriggerApplicationSnapShotDumper,      (SnapShotDumpType dump_type, const ams::sf::InBuffer &arg))                                     \
-        AMS_SF_METHOD_INFO(C, H, 20, Result, GetShellEventObserver,                 (ams::sf::Out<std::shared_ptr<pgl::sf::IEventObserver>> out))
+        AMS_SF_METHOD_INFO(C, H, 20, Result, GetShellEventObserver,                 (ams::sf::Out<std::shared_ptr<pgl::sf::IEventObserver>> out))                                   \
+        AMS_SF_METHOD_INFO(C, H, 21, Result, Command21NotImplemented,               (ams::sf::Out<u64> out, u32 in, const ams::sf::InBuffer &buf1, const ams::sf::InBuffer &buf2))
 
     AMS_SF_DEFINE_INTERFACE(IShellInterface, AMS_PGL_I_SHELL_INTERFACE_INTERFACE_INFO);
 
diff --git a/libraries/libstratosphere/include/stratosphere/pgl/srv/pgl_srv_shell_interface.hpp b/libraries/libstratosphere/include/stratosphere/pgl/srv/pgl_srv_shell_interface.hpp
index 3487c550b..2bf5fdcc7 100644
--- a/libraries/libstratosphere/include/stratosphere/pgl/srv/pgl_srv_shell_interface.hpp
+++ b/libraries/libstratosphere/include/stratosphere/pgl/srv/pgl_srv_shell_interface.hpp
@@ -47,6 +47,7 @@ namespace ams::pgl::srv {
             Result TriggerApplicationSnapShotDumper(SnapShotDumpType dump_type, const ams::sf::InBuffer &arg);
 
             Result GetShellEventObserver(ams::sf::Out<std::shared_ptr<pgl::sf::IEventObserver>> out);
+            Result Command21NotImplemented(ams::sf::Out<u64> out, u32 in, const ams::sf::InBuffer &buf1, const ams::sf::InBuffer &buf2);
     };
     static_assert(pgl::sf::IsIShellInterface<ShellInterface>);
 
diff --git a/libraries/libstratosphere/source/pgl/srv/pgl_srv_shell_interface.cpp b/libraries/libstratosphere/source/pgl/srv/pgl_srv_shell_interface.cpp
index 81b2641d5..56c618dc8 100644
--- a/libraries/libstratosphere/source/pgl/srv/pgl_srv_shell_interface.cpp
+++ b/libraries/libstratosphere/source/pgl/srv/pgl_srv_shell_interface.cpp
@@ -89,4 +89,8 @@ namespace ams::pgl::srv {
         return ResultSuccess();
     }
 
-}
\ No newline at end of file
+    Result ShellInterface::Command21NotImplemented(ams::sf::Out<u64> out, u32 in, const ams::sf::InBuffer &buf1, const ams::sf::InBuffer &buf2) {
+        return pgl::ResultNotImplemented();
+    }
+
+}
diff --git a/libraries/libvapours/include/vapours/results/pgl_results.hpp b/libraries/libvapours/include/vapours/results/pgl_results.hpp
index 93e4eb1a4..0cac357e2 100644
--- a/libraries/libvapours/include/vapours/results/pgl_results.hpp
+++ b/libraries/libvapours/include/vapours/results/pgl_results.hpp
@@ -21,6 +21,7 @@ namespace ams::pgl {
 
     R_DEFINE_NAMESPACE_RESULT_MODULE(228);
 
+    R_DEFINE_ERROR_RESULT(NotImplemented,             1);
     R_DEFINE_ERROR_RESULT(NotAvailable,               2);
     R_DEFINE_ERROR_RESULT(ApplicationNotRunning,      3);
     R_DEFINE_ERROR_RESULT(BufferNotEnough,            4);