diff --git a/autoload/neomake.vim b/autoload/neomake.vim
index 961bdcf3b2..4dee1abc6b 100644
--- a/autoload/neomake.vim
+++ b/autoload/neomake.vim
@@ -1319,10 +1319,8 @@ function! s:AddExprCallback(jobinfo, prev_list) abort
             if debug
                 call neomake#utils#DebugMessage(printf(
                   \ 'Modified list entry (postprocess): %s.',
-                  \ join(values(map(neomake#utils#diff_dict(before, entry)[0],
-                  \ "v:key.': '.string(v:val[0]).' => '.string(v:val[1])")))),
+                  \ string(neomake#utils#diff_dict(before, entry))),
                   \ a:jobinfo)
-
             endif
         endif
 
diff --git a/autoload/neomake/utils.vim b/autoload/neomake/utils.vim
index a0df595f8a..4c9837dc8a 100644
--- a/autoload/neomake/utils.vim
+++ b/autoload/neomake/utils.vim
@@ -533,16 +533,25 @@ function! neomake#utils#hook(event, context, ...) abort
     endif
 endfunction
 
-function! neomake#utils#diff_dict(d1, d2) abort
-    let diff = [{}, {}, {}]
-    let keys = keys(a:d1) + keys(a:d2)
+function! neomake#utils#diff_dict(old, new) abort
+    let diff = {}
+    let keys = keys(a:old) + keys(a:new)
     for k in keys
-        if !has_key(a:d2, k)
-            let diff[1][k] = a:d1[k]
-        elseif !has_key(a:d1, k)
-            let diff[2][k] = a:d2[k]
-        elseif type(a:d1[k]) !=# type(a:d2[k]) || a:d1[k] !=# a:d2[k]
-            let diff[0][k] = [a:d1[k], a:d2[k]]
+        if !has_key(a:new, k)
+            if !has_key(diff, 'removed')
+                let diff['removed'] = {}
+            endif
+            let diff['removed'][k] = a:old[k]
+        elseif !has_key(a:old, k)
+            if !has_key(diff, 'added')
+                let diff['added'] = {}
+            endif
+            let diff['added'][k] = a:new[k]
+        elseif type(a:old[k]) !=# type(a:new[k]) || a:old[k] !=# a:new[k]
+            if !has_key(diff, 'changed')
+                let diff['changed'] = {}
+            endif
+            let diff['changed'][k] = [a:old[k], a:new[k]]
         endif
     endfor
     return diff
diff --git a/tests/lists.vader b/tests/lists.vader
index f2098c46f5..d3136cec48 100644
--- a/tests/lists.vader
+++ b/tests/lists.vader
@@ -66,7 +66,7 @@ Execute (AddExprCallback with changed windows inbetween):
     wincmd k
     AssertEqual map(getloclist(0), 'v:val.text'), ['2 SUFFIX:1']
     bwipe
-    AssertNeomakeMessage "Modified list entry (postprocess): text: '2' => '2 SUFFIX:1'."
+    AssertNeomakeMessage "Modified list entry (postprocess): {'changed': {'text': ['2', '2 SUFFIX:1']}}."
   endif
 
 Execute (Goes back to original window after opening list):
diff --git a/tests/tempfiles.vader b/tests/tempfiles.vader
index ccc41ace81..eff0ab2811 100644
--- a/tests/tempfiles.vader
+++ b/tests/tempfiles.vader
@@ -441,7 +441,7 @@ Execute (Temporary buffer is not wiped if opened):
   exe 'bwipe' unlisted_bufnr
 
   AssertNeomakeMessage '\v^Setting bufnr according to tempfile for entry: .* ''bufnr'': '.tempfile_bufnr
-  AssertNeomakeMessage 'Modified list entry (postprocess): bufnr: '.tempfile_bufnr.' => '.bufnr.'.'
+  AssertNeomakeMessage printf("Modified list entry (postprocess): {'changed': {'bufnr': [%d, %d]}}.", tempfile_bufnr, bufnr)
   AssertNeomakeMessage 'WARN: seen entries with bufnr different from jobinfo.bufnr ('.bufnr.'): {'''.unlisted_bufnr.''': 1}, current bufnr: '.bufnr.'.'
 
 Execute (unlisted buffers created for tempfiles get wiped):
diff --git a/tests/utils.vader b/tests/utils.vader
index 1ba5b71ae2..896444c192 100644
--- a/tests/utils.vader
+++ b/tests/utils.vader
@@ -334,18 +334,18 @@ Execute (neomake#utils#ExpandArgs):
   bwipe
 
 Execute (neomake#utils#diff_dict):
-  AssertEqual neomake#utils#diff_dict({}, {}), [{}, {}, {}]
+  AssertEqual neomake#utils#diff_dict({}, {}), {}
   AssertEqual neomake#utils#diff_dict({'a': 1}, {'a': 2}),
-    \ [{'a': [1, 2]}, {}, {}]
+    \ {'changed': {'a': [1, 2]}}
   AssertEqual neomake#utils#diff_dict({'a': 1}, {'b': 2}),
-    \ [{}, {'a': 1}, {'b': 2}]
+    \ {'removed': {'a': 1}, 'added': {'b': 2}}
   AssertEqual neomake#utils#diff_dict({'a': 1}, {'a': 1, 'b': 2}),
-    \ [{}, {}, {'b': 2}]
+    \ {'added': {'b': 2}}
 
   AssertEqual neomake#utils#diff_dict({'a': '1'}, {'a': 1}),
-    \ [{'a': ['1', 1]}, {}, {}]
+    \ {'changed': {'a': ['1', 1]}}
   AssertEqual neomake#utils#diff_dict({'a': []}, {'a': {}}),
-    \ [{'a': [[], {}]}, {}, {}]
+    \ {'changed': {'a': [[], {}]}}
 
 Execute (neomake#utils#wstrpart):
   AssertEqual neomake#utils#wstrpart('123', 0, 0), ''