diff --git a/app/models/merge_request.rb b/app/models/merge_request.rb
index 8d3780532f39f59da3cb751d641981c59fb89973..6ce944173cd8f7189ed394b3dd93cb511730b440 100644
--- a/app/models/merge_request.rb
+++ b/app/models/merge_request.rb
@@ -172,6 +172,12 @@ class MergeRequest < ActiveRecord::Base
 
   def reloaded_commits
     if opened? && unmerged_commits.any?
+      # we need to reset st_commits field first
+      # in order to prevent internal rails comparison
+      self.st_commits = []
+      save
+
+      # Then we can safely write unmerged commits
       self.st_commits = unmerged_commits
       save
     end