diff --git a/Tools/ProtoProxy/Connection.cpp b/Tools/ProtoProxy/Connection.cpp
index de67c6e43..e91b9935e 100644
--- a/Tools/ProtoProxy/Connection.cpp
+++ b/Tools/ProtoProxy/Connection.cpp
@@ -249,10 +249,12 @@ void cConnection::Run(void)
 
 void cConnection::Log(const char * a_Format, ...)
 {
-	va_list args;
+	va_list args, argsCopy;
 	va_start(args, a_Format);
+	va_start(argsCopy, a_Format);
 	AString msg;
-	AppendVPrintf(msg, a_Format, args);
+	AppendVPrintf(msg, a_Format, args, argsCopy);
+	va_end(argsCopy);
 	va_end(args);
 	AString FullMsg;
 	Printf(FullMsg, "[%5.3f] %s\n", GetRelativeTime(), msg.c_str());
@@ -274,10 +276,12 @@ void cConnection::Log(const char * a_Format, ...)
 
 void cConnection::DataLog(const void * a_Data, int a_Size, const char * a_Format, ...)
 {
-	va_list args;
+	va_list args, argsCopy;
 	va_start(args, a_Format);
+	va_start(argsCopy, a_Format);
 	AString msg;
-	AppendVPrintf(msg, a_Format, args);
+	AppendVPrintf(msg, a_Format, args, argsCopy);
+	va_end(argsCopy);
 	va_end(args);
 	AString FullMsg;
 	AString Hex;
diff --git a/lib/inifile/iniFile.cpp b/lib/inifile/iniFile.cpp
index afa1c110d..c118eecaa 100644
--- a/lib/inifile/iniFile.cpp
+++ b/lib/inifile/iniFile.cpp
@@ -446,10 +446,12 @@ bool cIniFile::SetValueF(const AString & a_KeyName, const AString & a_ValueName,
 
 bool cIniFile::SetValueV(const AString & a_KeyName, const AString & a_ValueName, const char * a_Format, ...)
 {
-	va_list args;
+	va_list args, argsCopy;
 	va_start(args, a_Format);
+	va_start(argsCopy, a_Format);
 	AString Data;
-	AppendVPrintf(Data, a_Format, args);
+	AppendVPrintf(Data, a_Format, args, argsCopy);
+	va_end(argsCopy);
 	va_end(args);
 	return SetValue(a_KeyName, a_ValueName, Data);
 }
diff --git a/src/CommandOutput.cpp b/src/CommandOutput.cpp
index c221682a1..48a695969 100644
--- a/src/CommandOutput.cpp
+++ b/src/CommandOutput.cpp
@@ -16,9 +16,11 @@
 void cCommandOutputCallback::Out(const char * a_Fmt, ...)
 {
 	AString Output;
-	va_list args;
+	va_list args, argsCopy;
 	va_start(args, a_Fmt);
-	AppendVPrintf(Output, a_Fmt, args);
+	va_start(argsCopy, a_Fmt);
+	AppendVPrintf(Output, a_Fmt, args, argsCopy);
+	va_end(argsCopy);
 	va_end(args);
 	Output.append("\n");
 	Out(Output);
diff --git a/src/Log.cpp b/src/Log.cpp
index a0de4531b..8f811f14f 100644
--- a/src/Log.cpp
+++ b/src/Log.cpp
@@ -99,10 +99,10 @@ void cLog::ClearLog()
 
 
 
-void cLog::Log(const char * a_Format, va_list argList)
+void cLog::Log(const char * a_Format, va_list argList, va_list argListCopy)
 {
 	AString Message;
-	AppendVPrintf(Message, a_Format, argList);
+	AppendVPrintf(Message, a_Format, argList, argListCopy);
 
 	time_t rawtime;
 	time ( &rawtime );
@@ -147,11 +147,13 @@ void cLog::Log(const char * a_Format, va_list argList)
 
 
 
-void cLog::Log(const char* a_Format, ...)
+void cLog::Log(const char * a_Format, ...)
 {
-	va_list argList;
+	va_list argList, argListCopy;
 	va_start(argList, a_Format);
-	Log( a_Format, argList );
+	va_start(argListCopy, a_Format);
+	Log(a_Format, argList, argListCopy);
+	va_end(argListCopy);
 	va_end(argList);
 }
 
@@ -159,9 +161,9 @@ void cLog::Log(const char* a_Format, ...)
 
 
 
-void cLog::SimpleLog(const char* a_String)
+void cLog::SimpleLog(const char * a_String)
 {
-	Log("%s", a_String );
+	Log("%s", a_String);
 }
 
 
diff --git a/src/Log.h b/src/Log.h
index d00022c6f..d33fc2871 100644
--- a/src/Log.h
+++ b/src/Log.h
@@ -14,11 +14,11 @@ private:
 public:
 	cLog(const AString & a_FileName);
 	~cLog();
-	void Log(const char* a_Format, va_list argList );
-	void Log(const char* a_Format, ...);
+	void Log(const char * a_Format, va_list argList, va_list argListCopy);
+	void Log(const char * a_Format, ...);
 	// tolua_begin
-	void SimpleLog(const char* a_String);
-	void OpenLog( const char* a_FileName );
+	void SimpleLog(const char * a_String);
+	void OpenLog(const char * a_FileName);
 	void CloseLog();
 	void ClearLog();
 	static cLog* GetInstance();
diff --git a/src/OSSupport/File.cpp b/src/OSSupport/File.cpp
index 9f7c0d439..a55346c48 100644
--- a/src/OSSupport/File.cpp
+++ b/src/OSSupport/File.cpp
@@ -440,9 +440,11 @@ AString cFile::ReadWholeFile(const AString & a_FileName)
 int cFile::Printf(const char * a_Fmt, ...)
 {
 	AString buf;
-	va_list args;
+	va_list args, argsCopy;
 	va_start(args, a_Fmt);
-	AppendVPrintf(buf, a_Fmt, args);
+	va_start(argsCopy, a_Fmt);
+	AppendVPrintf(buf, a_Fmt, args, argsCopy);
+	va_end(argsCopy);
 	va_end(args);
 	return Write(buf.c_str(), buf.length());
 }
diff --git a/src/StringUtils.cpp b/src/StringUtils.cpp
index 2dcd9fec9..16937c8a2 100644
--- a/src/StringUtils.cpp
+++ b/src/StringUtils.cpp
@@ -18,7 +18,7 @@
 
 
 
-AString & AppendVPrintf(AString & str, const char *format, va_list args)
+AString & AppendVPrintf(AString & str, const char *format, va_list args, va_list argsCopy)
 {
 	ASSERT(format != NULL);
 	
@@ -28,10 +28,6 @@ AString & AppendVPrintf(AString & str, const char *format, va_list args)
 	// MS CRT provides secure printf that doesn't behave like in the C99 standard
 	if ((len = _vsnprintf_s(buffer, ARRAYCOUNT(buffer), _TRUNCATE, format, args)) != -1)
 	#else  // _MSC_VER
-	// We need to store a copy of the args, because on AMD64 in GCC the vsnprintf() is allowed to make changes to it (WTF?)
-	// Ref.: issue #541, http://www.bailopan.net/blog/?p=30
-	va_list args2;
-	va_copy(args2, args);
 	if ((len = vsnprintf(buffer, ARRAYCOUNT(buffer), format, args)) < ARRAYCOUNT(buffer))
 	#endif  // else _MSC_VER
 	{
@@ -53,9 +49,9 @@ AString & AppendVPrintf(AString & str, const char *format, va_list args)
 	// Allocate a buffer and printf into it:
 	std::vector<char> Buffer(len + 1);
 	#ifdef _MSC_VER
-	vsprintf_s((char *)&(Buffer.front()), Buffer.size(), format, args);
+	vsprintf_s((char *)&(Buffer.front()), Buffer.size(), format, argsCopy);
 	#else  // _MSC_VER
-	vsnprintf((char *)&(Buffer.front()), Buffer.size(), format, args2);
+	vsnprintf((char *)&(Buffer.front()), Buffer.size(), format, argsCopy);
 	#endif  // else _MSC_VER
 	str.append(&(Buffer.front()), Buffer.size() - 1);
 	return str;
@@ -68,9 +64,11 @@ AString & AppendVPrintf(AString & str, const char *format, va_list args)
 AString & Printf(AString & str, const char * format, ...)
 {
 	str.clear();
-	va_list args;
+	va_list args, argsCopy;
 	va_start(args, format);
-	std::string &retval = AppendVPrintf(str, format, args);
+	va_start(argsCopy, format);
+	std::string &retval = AppendVPrintf(str, format, args, argsCopy);
+	va_end(argsCopy);
 	va_end(args);
 	return retval;
 }
@@ -82,9 +80,11 @@ AString & Printf(AString & str, const char * format, ...)
 AString Printf(const char * format, ...)
 {
 	AString res;
-	va_list args;
+	va_list args, argsCopy;
 	va_start(args, format);
-	AppendVPrintf(res, format, args);
+	va_start(argsCopy, format);
+	AppendVPrintf(res, format, args, argsCopy);
+	va_end(argsCopy);
 	va_end(args);
 	return res;
 }
@@ -95,9 +95,11 @@ AString Printf(const char * format, ...)
 
 AString & AppendPrintf(AString &str, const char *format, ...)
 {
-	va_list args;
+	va_list args, argsCopy;
 	va_start(args, format);
-	std::string &retval = AppendVPrintf(str, format, args);
+	va_start(argsCopy, format);
+	std::string &retval = AppendVPrintf(str, format, args, argsCopy);
+	va_end(argsCopy);
 	va_end(args);
 	return retval;
 }
diff --git a/src/StringUtils.h b/src/StringUtils.h
index 2373f3843..35faeb01b 100644
--- a/src/StringUtils.h
+++ b/src/StringUtils.h
@@ -21,8 +21,12 @@ typedef std::list<AString>   AStringList;
 
 
 
-/// Add the formated string to the existing data in the string
-extern AString & AppendVPrintf(AString & str, const char * format, va_list args);
+/** Add the formated string to the existing data in the string
+It is silly to need to specify the arguments twice, but it is required for x64 / GCC:
+Ref.: issue #541, http://www.bailopan.net/blog/?p=30
+va_copy is not available until C++11, so we need to make do with passing a duplicate.
+*/
+extern AString & AppendVPrintf(AString & str, const char * format, va_list args, va_list argsCopy);
 
 /// Output the formatted text into the string
 extern AString & Printf       (AString & str, const char * format, ...);