diff --git a/stepmania/src/RageUtil.cpp b/stepmania/src/RageUtil.cpp
index e5e5c46e5b..2887d0377f 100644
--- a/stepmania/src/RageUtil.cpp
+++ b/stepmania/src/RageUtil.cpp
@@ -361,6 +361,47 @@ RString vssprintf( const char *szFormat, va_list argList )
 	return sStr;
 }
 
+/* Windows uses %I64i to format a 64-bit int, instead of %lli.  Convert "a b %lli %-3llu c d"
+ * to "a b %I64 %-3I64u c d".  This assumes a well-formed format string; invalid format strings
+ * should not crash, but the results are undefined. */
+#if defined(WIN32)
+RString ConvertI64FormatString( const RString &sStr )
+{
+	RString sRet;
+	sRet.reserve( sStr.size() + 16 );
+
+	size_t iOffset = 0;
+	while( iOffset < sStr.size() )
+	{
+		size_t iPercent = sStr.find( '%', iOffset );
+		if( iPercent != sStr.npos )
+		{
+			sRet.append( sStr, iOffset, iPercent - iOffset );
+			iOffset = iPercent;
+		}
+
+		size_t iEnd = sStr.find_first_of( "diouxXeEfFgGaAcsCSpnm%", iOffset + 1 );
+		if( iEnd != sStr.npos && iEnd - iPercent >= 3 && iPercent > 2 && sStr[iEnd-2] == 'l' && sStr[iEnd-1] == 'l' )
+		{
+			sRet.append( sStr, iPercent, iEnd - iPercent - 2 ); // %
+			sRet.append( "I64" ); // %I64
+			sRet.append( sStr, iEnd, 1 ); // %I64i
+			iOffset = iEnd + 1;
+		}
+		else
+		{
+			if( iEnd == sStr.npos )
+				iEnd = sStr.size() - 1;
+			sRet.append( sStr, iOffset, iEnd - iOffset + 1 );
+			iOffset = iEnd + 1;
+		}
+	}
+	return sRet;
+}
+#else
+RString ConvertI64FormatString( const RString &sStr ) { return sStr; }
+#endif
+
 /* ISO-639-1 codes: http://www.loc.gov/standards/iso639-2/langcodes.html
  * native forms: http://people.w3.org/rishida/names/languages.html
  * We don't use 3-letter codes, so we don't bother supporting them. */
diff --git a/stepmania/src/RageUtil.h b/stepmania/src/RageUtil.h
index 8b5b03cbe5..ac14b240c4 100644
--- a/stepmania/src/RageUtil.h
+++ b/stepmania/src/RageUtil.h
@@ -351,6 +351,7 @@ struct tm GetLocalTime();
 
 RString ssprintf( const char *fmt, ...) PRINTF(1,2);
 RString vssprintf( const char *fmt, va_list argList );
+RString ConvertI64FormatString( const RString &sStr );
 
 /*
  * Splits a Path into 4 parts (Directory, Drive, Filename, Extention).  Supports UNC path names.