--- a/include/Scintilla.iface
+++ b/include/Scintilla.iface
@@ -1755,6 +1755,10 @@
 # Given a valid document position, return the next position taking code
 # page into account. Maximum value returned is the last position in the document.
 fun position PositionAfter=2418(position pos,)
+
+# Given a valid document position, return a position that differs in a number
+# of characters. Returned value is always between 0 and last position in document.
+fun position PositionRelative=2670(position pos, int relative)
 
 # Copy a range of text to the clipboard. Positions are clipped into the document.
 fun void CopyRange=2419(position start, position end)