diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -98,6 +98,13 @@
 
 More examples are given in the [`test/rendering`](./test/rendering) folder.
 
+## TODO list
+
+- Handle variable-width characters such as tabs or some unicode characters
+
+  For tabs, we may just resort to having the user fix a given number of
+  spaces in the `printDiagnostic` function.
+
 ## License
 
 This work is licensed under the BSD-3 clause license.
diff --git a/diagnose.cabal b/diagnose.cabal
--- a/diagnose.cabal
+++ b/diagnose.cabal
@@ -5,7 +5,7 @@
 -- see: https://github.com/sol/hpack
 
 name:           diagnose
-version:        1.6.3
+version:        1.6.4
 synopsis:       Beautiful error reporting done easily
 description:    This package provides a simple way of getting beautiful compiler/interpreter errors
                 using a very simple interface for the programmer.
diff --git a/src/Error/Diagnose/Position.hs b/src/Error/Diagnose/Position.hs
--- a/src/Error/Diagnose/Position.hs
+++ b/src/Error/Diagnose/Position.hs
@@ -31,6 +31,9 @@
 --   > data Located a
 --   >   = a :@ Position
 --   >   deriving (Show, Eq, Ord, Functor, Traversable)
+--
+--   Columns are specified in amount of Unicode codepoints from the beginning of the line.
+--   Lines and columns start at 1.
 data Position = Position
   { -- | The beginning line and column of the span.
     begin :: (Int, Int),