diff --git a/src/details/os_windows.cpp b/src/details/os_windows.cpp
index 3267283f..2f0f1bde 100644
--- a/src/details/os_windows.cpp
+++ b/src/details/os_windows.cpp
@@ -200,7 +200,7 @@ bool in_terminal(FILE *file) noexcept { return ::_isatty(_fileno(file)) != 0; }
 
 #if defined(SPDLOG_WCHAR_FILENAMES)
 void wstr_to_utf8buf(wstring_view_t wstr, memory_buf_t &target) {
-    if (wstr.size() > static_cast<size_t>((std::numeric_limits<int>::max)()) / 2 - 1) {
+    if (wstr.size() > static_cast<size_t>((std::numeric_limits<int>::max)()) / 4 - 1) {
         throw_spdlog_ex("UTF-16 string is too big to be converted to UTF-8");
     }
 
@@ -211,7 +211,7 @@ void wstr_to_utf8buf(wstring_view_t wstr, memory_buf_t &target) {
     }
 
     int result_size = static_cast<int>(target.capacity());
-    if ((wstr_size + 1) * 2 > result_size) {
+    if ((wstr_size + 1) * 4 > result_size) {
         result_size = ::WideCharToMultiByte(CP_UTF8, 0, wstr.data(), wstr_size, NULL, 0, NULL, NULL);
     }