diff --git a/autoload/ale/job.vim b/autoload/ale/job.vim
index 2e0b8ca..9cebcf5 100644
--- a/autoload/ale/job.vim
+++ b/autoload/ale/job.vim
@@ -36,7 +36,7 @@ function! ale#job#JoinNeovimOutput(job, last_line, data, mode, callback) abort
         let l:lines[0] = a:last_line . l:lines[0]
         let l:new_last_line = a:data[-1]
     else
-        let l:new_last_line = a:last_line . a:data[0]
+        let l:new_last_line = a:last_line . get(a:data, 0, '')
     endif
 
     for l:line in l:lines
diff --git a/test/test_line_join.vader b/test/test_line_join.vader
index c93b192..25cefbc 100644
--- a/test/test_line_join.vader
+++ b/test/test_line_join.vader
@@ -17,6 +17,12 @@ After:
   delfunction LineCallback
   delfunction RawCallback
 
+Execute (ALE should handle empty Lists for the lines):
+  let g:last_line = ale#job#JoinNeovimOutput(1, '', [], 'nl', function('LineCallback'))
+
+  AssertEqual [], g:lines
+  AssertEqual '', g:last_line
+
 Execute (ALE should pass on full lines for NeoVim):
   let g:last_line = ale#job#JoinNeovimOutput(1, '', ['x', 'y', ''], 'nl', function('LineCallback'))