diff --git a/frmts/gtiff/libtiff/tif_dir.h b/frmts/gtiff/libtiff/tif_dir.h
index f4182a2cb7a5..ffad085e02ed 100644
--- a/frmts/gtiff/libtiff/tif_dir.h
+++ b/frmts/gtiff/libtiff/tif_dir.h
@@ -335,11 +335,10 @@ extern "C"
         TIFFDataType field_type; /* type of associated data */
         uint32_t
             field_anonymous; /* if true, this is a unknown / anonymous tag */
-        TIFFSetGetFieldType
-            set_field_type; /* type to be passed to TIFFSetField */
-        TIFFSetGetFieldType
-            get_field_type;              /* type to be passed to TIFFGetField */
-        unsigned short field_bit;        /* bit in fieldsset bit vector */
+        TIFFSetGetFieldType set_field_type; /* type to be passed to TIFFSetField
+                                               and TIFFGetField*/
+        TIFFSetGetFieldType get_field_type; /* not used */
+        unsigned short field_bit;           /* bit in fieldsset bit vector */
         unsigned char field_oktochange;  /* if true, can change while writing */
         unsigned char field_passcount;   /* if true, pass dir count on set */
         char *field_name;                /* ASCII name */
diff --git a/frmts/gtiff/libtiff/tif_dirwrite.c b/frmts/gtiff/libtiff/tif_dirwrite.c
index 0701f40d97ef..facdeaf7b161 100644
--- a/frmts/gtiff/libtiff/tif_dirwrite.c
+++ b/frmts/gtiff/libtiff/tif_dirwrite.c
@@ -869,7 +869,7 @@ static int TIFFWriteDirectorySec(TIFF *tif, int isimage, int imagedone,
                     if ((o->field_bit >= FIELD_CODEC) &&
                         (TIFFFieldSet(tif, o->field_bit)))
                     {
-                        switch (o->get_field_type)
+                        switch (o->set_field_type)
                         {
                             case TIFF_SETGET_ASCII:
                             {