diff --git a/plugins/s3_auth/s3_auth.cc b/plugins/s3_auth/s3_auth.cc
index d8d82449a56..3f47d8c6925 100644
--- a/plugins/s3_auth/s3_auth.cc
+++ b/plugins/s3_auth/s3_auth.cc
@@ -722,6 +722,7 @@ S3Request::set_header(const char *header, int header_len, const char *val, int v
     bool first = true;
 
     while (field_loc) {
+      tmp = TSMimeHdrFieldNextDup(_bufp, _hdr_loc, field_loc);
       if (first) {
         first = false;
         if (TS_SUCCESS == TSMimeHdrFieldValueStringSet(_bufp, _hdr_loc, field_loc, -1, val, val_len)) {
@@ -730,7 +731,6 @@ S3Request::set_header(const char *header, int header_len, const char *val, int v
       } else {
         TSMimeHdrFieldDestroy(_bufp, _hdr_loc, field_loc);
       }
-      tmp = TSMimeHdrFieldNextDup(_bufp, _hdr_loc, field_loc);
       TSHandleMLocRelease(_bufp, _hdr_loc, field_loc);
       field_loc = tmp;
     }