diff --git a/plugins/background_fetch/headers.cc b/plugins/background_fetch/headers.cc
index 4043993f3e6..19314c45ded 100644
--- a/plugins/background_fetch/headers.cc
+++ b/plugins/background_fetch/headers.cc
@@ -75,6 +75,7 @@ set_header(TSMBuffer bufp, TSMLoc hdr_loc, const char *header, int len, const ch
     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)) {
@@ -83,7 +84,6 @@ set_header(TSMBuffer bufp, TSMLoc hdr_loc, const char *header, int len, const ch
       } else {
         TSMimeHdrFieldDestroy(bufp, hdr_loc, field_loc);
       }
-      tmp = TSMimeHdrFieldNextDup(bufp, hdr_loc, field_loc);
       TSHandleMLocRelease(bufp, hdr_loc, field_loc);
       field_loc = tmp;
     }
diff --git a/plugins/experimental/access_control/headers.cc b/plugins/experimental/access_control/headers.cc
index fda3a74501d..4f78be92365 100644
--- a/plugins/experimental/access_control/headers.cc
+++ b/plugins/experimental/access_control/headers.cc
@@ -156,6 +156,7 @@ setHeader(TSMBuffer bufp, TSMLoc hdrLoc, const char *header, int headerlen, cons
     bool first = true;
 
     while (fieldLoc) {
+      tmp = TSMimeHdrFieldNextDup(bufp, hdrLoc, fieldLoc);
       if (first) {
         first = false;
         if (TS_SUCCESS == TSMimeHdrFieldValueStringSet(bufp, hdrLoc, fieldLoc, -1, value, valuelen)) {
@@ -164,7 +165,6 @@ setHeader(TSMBuffer bufp, TSMLoc hdrLoc, const char *header, int headerlen, cons
       } else {
         TSMimeHdrFieldDestroy(bufp, hdrLoc, fieldLoc);
       }
-      tmp = TSMimeHdrFieldNextDup(bufp, hdrLoc, fieldLoc);
       TSHandleMLocRelease(bufp, hdrLoc, fieldLoc);
       fieldLoc = tmp;
     }
diff --git a/plugins/experimental/cache_fill/background_fetch.cc b/plugins/experimental/cache_fill/background_fetch.cc
index e420220ce53..23e2e13ae8e 100644
--- a/plugins/experimental/cache_fill/background_fetch.cc
+++ b/plugins/experimental/cache_fill/background_fetch.cc
@@ -68,6 +68,7 @@ set_header(TSMBuffer bufp, TSMLoc hdr_loc, const char *header, int len, const ch
     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)) {
@@ -76,7 +77,6 @@ set_header(TSMBuffer bufp, TSMLoc hdr_loc, const char *header, int len, const ch
       } else {
         TSMimeHdrFieldDestroy(bufp, hdr_loc, field_loc);
       }
-      tmp = TSMimeHdrFieldNextDup(bufp, hdr_loc, field_loc);
       TSHandleMLocRelease(bufp, hdr_loc, field_loc);
       field_loc = tmp;
     }
diff --git a/plugins/experimental/cache_range_requests/cache_range_requests.cc b/plugins/experimental/cache_range_requests/cache_range_requests.cc
index cf2e04fc7c7..5b43d45fc16 100644
--- a/plugins/experimental/cache_range_requests/cache_range_requests.cc
+++ b/plugins/experimental/cache_range_requests/cache_range_requests.cc
@@ -433,6 +433,7 @@ set_header(TSMBuffer buf, TSMLoc hdr_loc, const char *header, int len, const cha
     bool first = true;
 
     while (field_loc) {
+      tmp = TSMimeHdrFieldNextDup(buf, hdr_loc, field_loc);
       if (first) {
         first = false;
         if (TS_SUCCESS == TSMimeHdrFieldValueStringSet(buf, hdr_loc, field_loc, -1, val, val_len)) {
@@ -441,7 +442,6 @@ set_header(TSMBuffer buf, TSMLoc hdr_loc, const char *header, int len, const cha
       } else {
         TSMimeHdrFieldDestroy(buf, hdr_loc, field_loc);
       }
-      tmp = TSMimeHdrFieldNextDup(buf, hdr_loc, field_loc);
       TSHandleMLocRelease(buf, hdr_loc, field_loc);
       field_loc = tmp;
     }
diff --git a/plugins/experimental/prefetch/headers.cc b/plugins/experimental/prefetch/headers.cc
index 8233dc54063..83bbc9c3203 100644
--- a/plugins/experimental/prefetch/headers.cc
+++ b/plugins/experimental/prefetch/headers.cc
@@ -156,6 +156,7 @@ setHeader(TSMBuffer bufp, TSMLoc hdrLoc, const char *header, int headerlen, cons
     bool first = true;
 
     while (fieldLoc) {
+      tmp = TSMimeHdrFieldNextDup(bufp, hdrLoc, fieldLoc);
       if (first) {
         first = false;
         if (TS_SUCCESS == TSMimeHdrFieldValueStringSet(bufp, hdrLoc, fieldLoc, -1, value, valuelen)) {
@@ -164,7 +165,6 @@ setHeader(TSMBuffer bufp, TSMLoc hdrLoc, const char *header, int headerlen, cons
       } else {
         TSMimeHdrFieldDestroy(bufp, hdrLoc, fieldLoc);
       }
-      tmp = TSMimeHdrFieldNextDup(bufp, hdrLoc, fieldLoc);
       TSHandleMLocRelease(bufp, hdrLoc, fieldLoc);
       fieldLoc = tmp;
     }
diff --git a/plugins/header_rewrite/operators.cc b/plugins/header_rewrite/operators.cc
index f8c39a74b1e..5ee06f13a14 100644
--- a/plugins/header_rewrite/operators.cc
+++ b/plugins/header_rewrite/operators.cc
@@ -621,6 +621,7 @@ OperatorSetHeader::exec(const Resources &res) const
       bool first = true;
 
       while (field_loc) {
+        tmp = TSMimeHdrFieldNextDup(res.bufp, res.hdr_loc, field_loc);
         if (first) {
           first = false;
           if (TS_SUCCESS == TSMimeHdrFieldValueStringSet(res.bufp, res.hdr_loc, field_loc, -1, value.c_str(), value.size())) {
@@ -629,7 +630,6 @@ OperatorSetHeader::exec(const Resources &res) const
         } else {
           TSMimeHdrFieldDestroy(res.bufp, res.hdr_loc, field_loc);
         }
-        tmp = TSMimeHdrFieldNextDup(res.bufp, res.hdr_loc, field_loc);
         TSHandleMLocRelease(res.bufp, res.hdr_loc, field_loc);
         field_loc = tmp;
       }