diff --git a/lib/lua/TCompactProtocol.lua b/lib/lua/TCompactProtocol.lua
index 8e7db8e..ca488dc 100644
--- a/lib/lua/TCompactProtocol.lua
+++ b/lib/lua/TCompactProtocol.lua
@@ -118,8 +118,8 @@
 end
 
 function TCompactProtocol:writeStructBegin(name)
-  self.lastFieldIndex = self.lastFieldIndex + 1
   self.lastField[self.lastFieldIndex] = self.lastFieldId
+  self.lastFieldIndex = self.lastFieldIndex + 1
   self.lastFieldId = 0
 end