diff --git a/db/migrate/20171103000000_set_uploads_path_size_for_mysql.rb b/db/migrate/20171103000000_set_uploads_path_size_for_mysql.rb
new file mode 100644
index 0000000000000000000000000000000000000000..1fbe505f804b8259ecbe0a3b0f87435f92f42830
--- /dev/null
+++ b/db/migrate/20171103000000_set_uploads_path_size_for_mysql.rb
@@ -0,0 +1,25 @@
+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class SetUploadsPathSizeForMysql < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  # Set this constant to true if this migration requires downtime.
+  DOWNTIME = false
+
+  def up
+    # We need at least 297 at the moment. For more detail on that number, see:
+    # https://gitlab.com/gitlab-org/gitlab-ce/issues/40168#what-is-the-expected-correct-behavior
+    #
+    # Rails + PostgreSQL `string` is equivalent to a `text` field, but
+    # Rails + MySQL `string` is `varchar(255)` by default. Also, note that we
+    # have an upper limit because with a unique index, MySQL has a max key
+    # length of 3072 bytes which seems to correspond to `varchar(1024)`.
+    change_column :uploads, :path, :string, limit: 511
+  end
+
+  def down
+    # It was unspecified, which is varchar(255) by default in Rails for MySQL.
+    change_column :uploads, :path, :string
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index effb2604af2e6fa0744d1d0a9a120be5528d00aa..fed7284a1a1cc20dc6816434a0f06a16cf38a4b5 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -1721,7 +1721,7 @@ ActiveRecord::Schema.define(version: 20171124150326) do
 
   create_table "uploads", force: :cascade do |t|
     t.integer "size", limit: 8, null: false
-    t.string "path", null: false
+    t.string "path", limit: 511, null: false
     t.string "checksum", limit: 64
     t.integer "model_id"
     t.string "model_type"