diff --git a/autoload/ale/highlight.vim b/autoload/ale/highlight.vim
index b51e5b2d..4ac1d1e4 100644
--- a/autoload/ale/highlight.vim
+++ b/autoload/ale/highlight.vim
@@ -86,7 +86,7 @@ function! ale#highlight#UpdateHighlights() abort
             let l:col = l:item.col
             let l:group = l:item.type ==# 'E' ? 'ALEError' : 'ALEWarning'
             let l:line = l:item.lnum
-            let l:size = has_key(l:item, 'end_col') ? l:item.end_col - l:col : 1
+            let l:size = has_key(l:item, 'end_col') ? l:item.end_col - l:col + 1 : 1
 
             " Rememeber the match ID for the item.
             " This ID will be used to preserve loclist items which are set
diff --git a/test/test_highlight_placement.vader b/test/test_highlight_placement.vader
index e43b0dc1..b5878922 100644
--- a/test/test_highlight_placement.vader
+++ b/test/test_highlight_placement.vader
@@ -146,7 +146,7 @@ Execute(Higlight end columns should set an appropriate size):
 
   AssertEqual
   \ [
-  \   {'group': 'ALEError', 'id': 15, 'priority': 10, 'pos1': [3, 2, 3]},
-  \   {'group': 'ALEWarning', 'id': 16, 'priority': 10, 'pos1': [4, 1, 4]},
+  \   {'group': 'ALEError', 'id': 15, 'priority': 10, 'pos1': [3, 2, 4]},
+  \   {'group': 'ALEWarning', 'id': 16, 'priority': 10, 'pos1': [4, 1, 5]},
   \ ],
   \ getmatches()