1 files changed, 6 insertions, 2 deletions

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, ...);