diff --git a/src/game/UpdateData.cpp b/src/game/UpdateData.cpp
index 546d84002..a01d82181 100644
--- a/src/game/UpdateData.cpp
+++ b/src/game/UpdateData.cpp
@@ -103,7 +103,7 @@ void UpdateData::Compress(void* dst, uint32 *dst_size, void* src, int src_size)
 
 bool UpdateData::BuildPacket(WorldPacket *packet)
 {
-    ByteBuffer buf(m_data.size());
+    ByteBuffer buf(4+(m_outOfRangeGUIDs.empty() ? 0 : 1+4+9*m_outOfRangeGUIDs.size())+m_data.wpos());
 
     buf << (uint32) (!m_outOfRangeGUIDs.empty() ? m_blockCount + 1 : m_blockCount);
 
@@ -122,15 +122,14 @@ bool UpdateData::BuildPacket(WorldPacket *packet)
 
     packet->clear();
 
-    size_t pSize = buf.size();
+    size_t pSize = buf.wpos();                              // use real used data size
 
     if (pSize > 100 )                                       // compress large packets
     {
-        packet->resize(pSize);
+        uint32 destsize = pSize;
+        packet->resize( destsize + sizeof(uint32) );
 
         packet->put<uint32>(0, pSize);
-
-        uint32 destsize = pSize;
         Compress(const_cast<uint8*>(packet->contents()) + sizeof(uint32), &destsize, (void*)buf.contents(), pSize);
         if (destsize == 0)
             return false;
diff --git a/src/shared/ByteBuffer.h b/src/shared/ByteBuffer.h
index c289d34a7..f109504ca 100644
--- a/src/shared/ByteBuffer.h
+++ b/src/shared/ByteBuffer.h
@@ -309,7 +309,7 @@ class ByteBuffer
         }
         void append(const ByteBuffer& buffer)
         {
-            if(buffer.size()) append(buffer.contents(),buffer.wpos());
+            if(buffer.wpos()) append(buffer.contents(),buffer.wpos());
         }
 
         void appendPackGUID(uint64 guid)
diff --git a/src/shared/revision_nr.h b/src/shared/revision_nr.h
index b24cf0818..8e23251aa 100644
--- a/src/shared/revision_nr.h
+++ b/src/shared/revision_nr.h
@@ -1,4 +1,4 @@
 #ifndef __REVISION_NR_H__
 #define __REVISION_NR_H__
- #define REVISION_NR "7967"
+ #define REVISION_NR "7968"
 #endif // __REVISION_NR_H__