diff --git a/include/core/nxdt_includes.h b/include/core/nxdt_includes.h
index ba6b415..ab55ae6 100644
--- a/include/core/nxdt_includes.h
+++ b/include/core/nxdt_includes.h
@@ -78,16 +78,21 @@
 #include "lz4.h"
 
 /// Used to store version numbers expressed in dot notation: "{major}.{minor}.{micro}-{major_relstep}.{minor_relstep}".
-/// Used by system version fields.
+/// Used by system version fields. 16-bit long relstep values were used by system version fields prior to HOS 3.0.0.
 typedef struct {
     union {
         u32 value;
         struct {
-            u32 minor_relstep : 8;
-            u32 major_relstep : 8;
-            u32 micro         : 4;
-            u32 minor         : 6;
-            u32 major         : 6;
+            union {
+                u16 relstep;
+                struct {
+                    u16 minor_relstep : 8;
+                    u16 major_relstep : 8;
+                };
+            };
+            u16 micro                 : 4;
+            u16 minor                 : 6;
+            u16 major                 : 6;
         };
     };
 } SystemVersion;
@@ -109,7 +114,7 @@ typedef struct {
 NXDT_ASSERT(ApplicationVersion, 0x4);
 
 /// Used to store version numbers expressed in dot notation: "{major}.{minor}.{micro}-{relstep}".
-/// Used by SDK version fields. This format was also used for system version fields prior to HOS 3.0.0.
+/// Used by SDK version fields.
 typedef struct {
     union {
         u32 value;
diff --git a/source/gamecard_tab.cpp b/source/gamecard_tab.cpp
index 3767808..ea6e1b5 100644
--- a/source/gamecard_tab.cpp
+++ b/source/gamecard_tab.cpp
@@ -162,14 +162,13 @@ namespace nxdt::views
         gamecardGetDecryptedCardInfoArea(&card_info);
 
         const SystemVersion upp_version = card_info.upp_version.system_version;
-        const SdkAddOnVersion upp_version_old = card_info.upp_version.sdk_addon_version;
 
         /* TODO: move somewhere else? */
-        if (upp_version_old.major == 0 && upp_version_old.minor == 0)
+        if (upp_version.major == 0 && upp_version.minor == 0)
         {
             std::string upp_version_display = "";
 
-            switch(upp_version_old.micro)
+            switch(upp_version.micro)
             {
                 case 0: /* v450 / 0.0.0-450 */
                     upp_version_display = "1.0.0";
@@ -192,11 +191,11 @@ namespace nxdt::views
 
             if (upp_version_display != "")
             {
-                update_version->setValue(fmt::format("{} ({}.{}.{}-{}) (v{})", upp_version_display, upp_version_old.major, upp_version_old.minor, upp_version_old.micro, \
-                                                                               upp_version_old.relstep, upp_version_old.value));
+                update_version->setValue(fmt::format("{} ({}.{}.{}-{}) (v{})", upp_version_display, upp_version.major, upp_version.minor, upp_version.micro, \
+                                                                               upp_version.relstep, upp_version.value));
             } else {
-                update_version->setValue(fmt::format("{}.{}.{}-{} (v{})", upp_version_old.major, upp_version_old.minor, upp_version_old.micro, \
-                                                                          upp_version_old.relstep, upp_version_old.value));
+                update_version->setValue(fmt::format("{}.{}.{}-{} (v{})", upp_version.major, upp_version.minor, upp_version.micro, \
+                                                                          upp_version.relstep, upp_version.value));
             }
         } else {
             update_version->setValue(fmt::format("{}.{}.{}-{}.{} (v{})", upp_version.major, upp_version.minor, upp_version.micro, \