Index: slnunico.c
===================================================================
--- slnunico.c	(revision 10089)
+++ slnunico.c	(working copy)
@@ -117,6 +117,8 @@
 #include "lauxlib.h"
 #include "lualib.h"
 
+#include <windows.h>
+
 /*
 ** maximum number of captures that a pattern can do during
 ** pattern-matching. This limit is arbitrary.
@@ -1661,6 +1663,7 @@
 				{
 					size_t l;
 					const char *s = luaL_checklstring(L, arg, &l);
+					int nw = MultiByteToWideChar(CP_UTF8, 0, s,l, NULL, 0);
 
 					if(!hasprecision && l >= 100)
 					{
@@ -1675,7 +1678,16 @@
 #ifdef LUA_USE_SNPRINTF
 						snprintf(buff, MAX_ITEM, form, s);
 #else
-						sprintf(buff, form, s);
+						if ((size_t)nw >= l)
+							sprintf(buff, form, s);
+						else {
+							wchar_t ws[100], wf[256], wb[512];
+							int nwo;
+							MultiByteToWideChar(CP_UTF8, 0, form,-1, wf, sizeof(wf)/sizeof(wf[0]));
+							MultiByteToWideChar(CP_UTF8, 0, s,-1, ws,	sizeof(ws)/sizeof(ws[0]));
+							nwo = _snwprintf_s(wb, sizeof(wb)/sizeof(wb[0]), sizeof(wb)/sizeof(wb[0]), wf, ws);
+							WideCharToMultiByte(CP_UTF8, 0, wb,-1, buff,MAX_ITEM, NULL, NULL);
+						}
 #endif
 						break;
 					}