diff --git a/Source/Core/Common/StringUtil.cpp b/Source/Core/Common/StringUtil.cpp
index c9100ff11a..f960d6fcc6 100644
--- a/Source/Core/Common/StringUtil.cpp
+++ b/Source/Core/Common/StringUtil.cpp
@@ -426,7 +426,7 @@ size_t StringUTF8CodePointCount(std::string_view str)
 
 #ifdef _WIN32
 
-std::wstring CPToUTF16(u32 code_page, std::string_view input)
+static std::wstring CPToUTF16(u32 code_page, std::string_view input)
 {
   auto const size =
       MultiByteToWideChar(code_page, 0, input.data(), static_cast<int>(input.size()), nullptr, 0);
@@ -444,7 +444,7 @@ std::wstring CPToUTF16(u32 code_page, std::string_view input)
   return output;
 }
 
-std::string UTF16ToCP(u32 code_page, std::wstring_view input)
+static std::string UTF16ToCP(u32 code_page, std::wstring_view input)
 {
   if (input.empty())
     return {};