diff --git a/plugins/header_rewrite/operators.cc b/plugins/header_rewrite/operators.cc
index fda921cf2be..da14d35fdc3 100644
--- a/plugins/header_rewrite/operators.cc
+++ b/plugins/header_rewrite/operators.cc
@@ -383,12 +383,11 @@ void
 OperatorAddHeader::exec(const Resources& res) const
 {
   std::string value;
+  _value.append_value(value, res);
 
   VariableExpander ve(value);
   value = ve.expand(res);
 
-  _value.append_value(value, res);
-
   // Never set an empty header (I don't think that ever makes sense?)
   if (value.empty()) {
     TSDebug(PLUGIN_NAME, "Would set header %s to an empty value, skipping", _header.c_str());