diff --git a/src/Dialogs.c b/src/Dialogs.c
index 4af3205d2..4e2ea81be 100644
--- a/src/Dialogs.c
+++ b/src/Dialogs.c
@@ -475,12 +475,13 @@ LONG InfoBoxLng(UINT uType, LPCWSTR lpstrSetting, UINT uidMsg, ...)
     msgBox.uType = uType;
     msgBox.lpstrMessage = AllocMem((COUNTOF(wchMessage)+1) * sizeof(WCHAR), HEAP_ZERO_MEMORY);
 
-    const PUINT_PTR argp = (PUINT_PTR)& uidMsg + 1;
-    if (argp && *argp) {
-        StringCchVPrintfW(msgBox.lpstrMessage, COUNTOF(wchMessage), wchMessage, (LPVOID)argp);
-    } else {
-        StringCchCopy(msgBox.lpstrMessage, COUNTOF(wchMessage), wchMessage);
-    }
+    // Use va_list (not the &uidMsg+1 stack-walk hack): on Windows ARM64 the first 8
+    // varargs are in registers X0–X7, not at &uidMsg+1, so the old code read garbage and
+    // typically fell through to the no-args branch — leaving literal "%s" in the message.
+    va_list args;
+    va_start(args, uidMsg);
+    StringCchVPrintfW(msgBox.lpstrMessage, COUNTOF(wchMessage), wchMessage, args);
+    va_end(args);
 
     bool bLastError = false;
     switch (uidMsg) {
diff --git a/src/MuiLanguage.c b/src/MuiLanguage.c
index a93a13c2c..8d2b5529c 100644
--- a/src/MuiLanguage.c
+++ b/src/MuiLanguage.c
@@ -644,7 +644,12 @@ int FormatLngStringW(LPWSTR lpOutput, int nOutput, UINT uIdFormat, ...)
     WCHAR* const pBuffer = AllocMem(sizeof(WCHAR) * nOutput, HEAP_ZERO_MEMORY);
     if (pBuffer) {
         if (LoadLngStringW(uIdFormat, pBuffer, nOutput)) {
-            StringCchVPrintfW(lpOutput, nOutput, pBuffer, (LPVOID)((PUINT_PTR)& uIdFormat + 1));
+            // va_list, not &uIdFormat+1 — the latter walks the stack and breaks on ARM64
+            // where the first 8 varargs are in X0–X7 registers.
+            va_list args;
+            va_start(args, uIdFormat);
+            StringCchVPrintfW(lpOutput, nOutput, pBuffer, args);
+            va_end(args);
         }
         FreeMem(pBuffer);
         return (int)StringCchLen(lpOutput, nOutput);
@@ -661,7 +666,10 @@ int FormatLngStringA(LPSTR lpOutput, int nOutput, UINT uIdFormat, ...)
     CHAR* const pBuffer = AllocMem(sizeof(CHAR) * nOutput, HEAP_ZERO_MEMORY);
     if (pBuffer) {
         if (LoadLngStringA(uIdFormat, pBuffer, nOutput)) {
-            StringCchVPrintfA(lpOutput, nOutput, pBuffer, (LPVOID)((PUINT_PTR)& uIdFormat + 1));
+            va_list args;
+            va_start(args, uIdFormat);
+            StringCchVPrintfA(lpOutput, nOutput, pBuffer, args);
+            va_end(args);
         }
         FreeMem(pBuffer);
         return (int)StringCchLenA(lpOutput, nOutput);