diff --git a/CHANGELOG b/CHANGELOG
index e93938054fe..8ff61cd6e9f 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -2,6 +2,7 @@ Please view this file on the master branch, on stable branches it's out of date.
 
 v 8.1.0 (unreleased)
   - Fix bug where projects would appear to be stuck in the forked import state (Stan Hu)
+  - Fix Error 500 in creating merge requests with > 1000 diffs (Stan Hu)
   - Show CI status on all pages where commits list is rendered
   - Automatically enable CI when push .gitlab-ci.yml file to repository
   - Move CI charts to project graphs area
diff --git a/app/models/merge_request_diff.rb b/app/models/merge_request_diff.rb
index e317c8eac4d..f75f999b0d0 100644
--- a/app/models/merge_request_diff.rb
+++ b/app/models/merge_request_diff.rb
@@ -123,12 +123,12 @@ class MergeRequestDiff < ActiveRecord::Base
     if new_diffs.any?
       if new_diffs.size > Commit::DIFF_HARD_LIMIT_FILES
         self.state = :overflow_diff_files_limit
-        new_diffs = new_diffs.first[Commit::DIFF_HARD_LIMIT_LINES]
+        new_diffs = new_diffs.first(Commit::DIFF_HARD_LIMIT_LINES)
       end
 
       if new_diffs.sum { |diff| diff.diff.lines.count } > Commit::DIFF_HARD_LIMIT_LINES
         self.state = :overflow_diff_lines_limit
-        new_diffs = new_diffs.first[Commit::DIFF_HARD_LIMIT_LINES]
+        new_diffs = new_diffs.first(Commit::DIFF_HARD_LIMIT_LINES)
       end
     end