diff --git a/windows/uipriv_windows.hpp b/windows/uipriv_windows.hpp
index 7c43874b..d0b84a8c 100644
--- a/windows/uipriv_windows.hpp
+++ b/windows/uipriv_windows.hpp
@@ -38,6 +38,7 @@ extern WCHAR *vstrf(const WCHAR *format, va_list ap);
 extern char *LFtoCRLF(const char *lfonly);
 extern void CRLFtoLF(const char *s);
 extern WCHAR *ftoutf16(double d);
+extern WCHAR *itoutf16(intmax_t i);
 
 // debug.cpp
 // see http://stackoverflow.com/questions/14421656/is-there-widely-available-wide-character-variant-of-file
diff --git a/windows/utf16.cpp b/windows/utf16.cpp
index 07fd4363..9acc5e82 100644
--- a/windows/utf16.cpp
+++ b/windows/utf16.cpp
@@ -140,3 +140,14 @@ WCHAR *ftoutf16(double d)
 	s = ss.str();		// to be safe
 	return utf16dup(s.c_str());
 }
+
+// to complement the above
+WCHAR *itoutf16(intmax_t i)
+{
+	std::wostringstream ss;
+	std::wstring s;
+
+	ss << i;
+	s = ss.str();		// to be safe
+	return utf16dup(s.c_str());
+}