diff --git a/arm9/source/config.c b/arm9/source/config.c
index ab91dbf6..5f54fb36 100644
--- a/arm9/source/config.c
+++ b/arm9/source/config.c
@@ -694,7 +694,7 @@ static size_t saveLumaIniConfigToStr(char *out)
     return n < 0 ? 0 : (size_t)n;
 }
 
-static char tmpIniBuffer[0x2000];
+static char tmpIniBuffer[0x2000 + 0x400]; // eyeballed. TODO use #embed
 
 static bool readLumaIniConfig(void)
 {
@@ -709,6 +709,13 @@ static bool readLumaIniConfig(void)
 static bool writeLumaIniConfig(void)
 {
     size_t n = saveLumaIniConfigToStr(tmpIniBuffer);
+
+    // FIXME: this is UB we should port snprintf sometime (as well as fix other tech debt)
+    if (n + 1 >= sizeof(tmpIniBuffer)) {
+        error("Configuration data buffer overflow, please report this issue");
+        __builtin_unreachable();
+    }
+
     return n != 0 && fileWrite(tmpIniBuffer, "config.ini", n);
 }
 
diff --git a/sysmodules/rosalina/include/utils.h b/sysmodules/rosalina/include/utils.h
index d9e77394..810caedb 100644
--- a/sysmodules/rosalina/include/utils.h
+++ b/sysmodules/rosalina/include/utils.h
@@ -30,6 +30,7 @@
 #include <3ds/srv.h>
 #include <3ds/result.h>
 #include <3ds/ipc.h>
+#include <assert.h>
 #include "csvc.h"
 #include "luma_shared_config.h"
 
diff --git a/sysmodules/rosalina/source/luma_config.c b/sysmodules/rosalina/source/luma_config.c
index 5b877474..7e949ecc 100644
--- a/sysmodules/rosalina/source/luma_config.c
+++ b/sysmodules/rosalina/source/luma_config.c
@@ -204,7 +204,7 @@ void LumaConfig_RequestSaveSettings(void) {
 
 Result LumaConfig_SaveSettings(void)
 {
-    char inibuf[0x2000];
+    char inibuf[0x2000 + 0x400]; // eyeballed. TODO use #embed
 
     Result res;
 
@@ -259,6 +259,12 @@ Result LumaConfig_SaveSettings(void)
     configData.autobootCtrAppmemtype = autobootCtrAppmemtype;
 
     size_t n = LumaConfig_SaveLumaIniConfigToStr(inibuf, &configData);
+
+    // FIXME: this is UB we should port snprintf sometime (as well as fix other tech debt in Rosalina)
+    if (n + 1 >= sizeof(inibuf)) {
+        __builtin_trap();
+    }
+
     FS_ArchiveID archiveId = isSdMode ? ARCHIVE_SDMC : ARCHIVE_NAND_RW;
     if (n > 0)
         res = IFile_Open(&file, archiveId, fsMakePath(PATH_EMPTY, ""), fsMakePath(PATH_ASCII, "/luma/config.ini"), FS_OPEN_CREATE | FS_OPEN_WRITE);