diff --git a/tdishr/TdiIo.c b/tdishr/TdiIo.c
index 3df35d0059..66729c504e 100644
--- a/tdishr/TdiIo.c
+++ b/tdishr/TdiIo.c
@@ -182,6 +182,27 @@ int Tdi1Fclose(opcode_t opcode __attribute__((unused)),
   return TdiPutLong((int *)&err, out_ptr);
 }
 
+mdsdsc_t * Tdi3SeekSet()
+{
+    static const int value = SEEK_SET;
+    static const mdsdsc_t constant = { sizeof(value), DTYPE_L, CLASS_S, (char *)&value };
+    return (mdsdsc_t *)&constant;
+}
+
+mdsdsc_t * Tdi3SeekCur()
+{
+    static const int value = SEEK_CUR;
+    static const mdsdsc_t constant = { sizeof(value), DTYPE_L, CLASS_S, (char *)&value };
+    return (mdsdsc_t *)&constant;
+}
+
+mdsdsc_t * Tdi3SeekEnd()
+{
+    static const int value = SEEK_END;
+    static const mdsdsc_t constant = { sizeof(value), DTYPE_L, CLASS_S, (char *)&value };
+    return (mdsdsc_t *)&constant;
+}
+
 /*----------------------------------------------
         Specify position of file pointer.
         err = FSEEK(unit, offset, origin)
diff --git a/tdishr/opcodes.csv b/tdishr/opcodes.csv
index 15827f8811..a24e92e851 100644
--- a/tdishr/opcodes.csv
+++ b/tdishr/opcodes.csv
@@ -460,3 +460,6 @@
 "458","List","LIST","List","undef","undef","XX","YY","XX","YY","0","254","OK+I+S","%f9+ [a..z1:z2:dz..n@[this]]"
 "459","Squeeze","SQUEEZE","Reshape","undef","undef","XX","YY","XX","YY","1","2","OK","%f9+ squeeze(array, [min ndim]) "
 "460","Flatten","FLATTEN","Reshape","undef","undef","XX","YY","XX","YY","1","1","OK","%f9+ flatten(array) "
+"461","SeekSet","$SEEK_SET","Constant","undef","SeekSet","VV","VV","VV","VV","0","0","CONST","SEEK_SET"
+"462","SeekCur","$SEEK_CUR","Constant","undef","SeekCur","VV","VV","VV","VV","0","0","CONST","SEEK_CUR"
+"463","SeekEnd","$SEEK_END","Constant","undef","SeekEnd","VV","VV","VV","VV","0","0","CONST","SEEK_END"