diff --git a/changelogs/unreleased/disallow-null-values-for-environments-project-id.yml b/changelogs/unreleased/disallow-null-values-for-environments-project-id.yml
new file mode 100644
index 0000000000000000000000000000000000000000..f4a956e67248be125117a4c2aa2478499303e3e9
--- /dev/null
+++ b/changelogs/unreleased/disallow-null-values-for-environments-project-id.yml
@@ -0,0 +1,5 @@
+---
+title: "Disallow NULL values for environments.project_id"
+merge_request:
+author:
+type: other
diff --git a/db/migrate/20170913131410_environments_project_id_not_null.rb b/db/migrate/20170913131410_environments_project_id_not_null.rb
new file mode 100644
index 0000000000000000000000000000000000000000..d5404f8ede9989b5947537489e713b1cf517fabb
--- /dev/null
+++ b/db/migrate/20170913131410_environments_project_id_not_null.rb
@@ -0,0 +1,16 @@
+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class EnvironmentsProjectIdNotNull < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  def up
+    change_column_null :environments, :project_id, false
+  end
+
+  def down
+    change_column_null :environments, :project_id, true
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index 2149f5ad23df0a8d17a55115c59bf6b6403a5605..dd0ef04788b6919c91318d520371f63d89f5b1e4 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20170905112933) do
+ActiveRecord::Schema.define(version: 20170913131410) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -520,7 +520,7 @@ ActiveRecord::Schema.define(version: 20170905112933) do
   add_index "emails", ["user_id"], name: "index_emails_on_user_id", using: :btree
 
   create_table "environments", force: :cascade do |t|
-    t.integer "project_id"
+    t.integer "project_id", null: false
     t.string "name", null: false
     t.datetime "created_at"
     t.datetime "updated_at"