diff --git a/CHANGELOG.md b/CHANGELOG.md
index 31d1455d..04cbbae9 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,6 @@
 ## Next Version
 
+* Ensure an application is started with the correct ENV - @eval
 * Accept -e and --environment options for `rails console`.
 * Watch `config/secrets.yml` by default. #289 - @morgoth
 * Custom Spring commands that implement `#binstub_prelude` will have that
diff --git a/lib/spring/application.rb b/lib/spring/application.rb
index 90d39dfc..d41917df 100644
--- a/lib/spring/application.rb
+++ b/lib/spring/application.rb
@@ -133,6 +133,24 @@ def run
       end
     end
 
+    def with_env_vars(env)
+      # Allowed are keys currently not in ENV...
+      allowed_keys = env.keys - ENV.keys
+      # ...and ENV-keys whose values have not changed since the start of spring
+      allowed_keys += original_env.select {|k, v| ENV[k] == v }.keys
+      # never allowed:
+      allowed_keys -= %w(RUBYOPT RUBY_ROOT BUNDLE_GEMFILE GEM_ROOT GEM_HOME GEM_PATH)
+      allowed_keys.uniq!
+
+      allowed_keys.each{|k| ENV[k] = env[k] }
+
+      yield
+    ensure
+      allowed_keys.each do |k|
+        original_env.has_key?(k) ? ENV[k] = original_env[k] : ENV.delete(k)
+      end
+    end
+
     def serve(client)
       log "got client"
       manager.puts
@@ -140,66 +158,63 @@ def serve(client)
       stdout, stderr, stdin = streams = 3.times.map { client.recv_io }
       [STDOUT, STDERR, STDIN].zip(streams).each { |a, b| a.reopen(b) }
 
-      preload unless preloaded?
+      client_args, client_env = JSON.load(client.read(client.gets.to_i)).values_at("args", "env")
 
-      args, env = JSON.load(client.read(client.gets.to_i)).values_at("args", "env")
-      command   = Spring.command(args.shift)
-
-      connect_database
-      setup command
-
-      if Rails.application.reloaders.any?(&:updated?)
-        ActionDispatch::Reloader.cleanup!
-        ActionDispatch::Reloader.prepare!
-      end
+      @pid = nil
+      with_env_vars(client_env) do
+        preload unless preloaded?
+        command = Spring.command(client_args.shift)
 
-      pid = fork {
-        IGNORE_SIGNALS.each { |sig| trap(sig, "DEFAULT") }
-        trap("TERM", "DEFAULT")
+        connect_database
+        setup command
 
-        ARGV.replace(args)
-        $0 = command.process_title
+        if Rails.application.reloaders.any?(&:updated?)
+          ActionDispatch::Reloader.cleanup!
+          ActionDispatch::Reloader.prepare!
+        end
 
-        # Delete all env vars which are unchanged from before spring started
-        original_env.each { |k, v| ENV.delete k if ENV[k] == v }
+        @pid = fork {
+          IGNORE_SIGNALS.each { |sig| trap(sig, "DEFAULT") }
+          trap("TERM", "DEFAULT")
 
-        # Load in the current env vars, except those which *were* changed when spring started
-        env.each { |k, v| ENV[k] ||= v }
+          ARGV.replace(client_args)
+          $0 = command.process_title
 
-        # requiring is faster, so if config.cache_classes was true in
-        # the environment's config file, then we can respect that from
-        # here on as we no longer need constant reloading.
-        if @original_cache_classes
-          ActiveSupport::Dependencies.mechanism = :require
-          Rails.application.config.cache_classes = true
-        end
+          # requiring is faster, so if config.cache_classes was true in
+          # the environment's config file, then we can respect that from
+          # here on as we no longer need constant reloading.
+          if @original_cache_classes
+            ActiveSupport::Dependencies.mechanism = :require
+            Rails.application.config.cache_classes = true
+          end
 
-        connect_database
-        srand
+          connect_database
+          srand
 
-        invoke_after_fork_callbacks
-        shush_backtraces
+          invoke_after_fork_callbacks
+          shush_backtraces
 
-        command.call
-      }
+          command.call
+        }
+      end
 
       disconnect_database
       reset_streams
 
-      log "forked #{pid}"
-      manager.puts pid
+      log "forked #{@pid}"
+      manager.puts @pid
 
-      wait pid, streams, client
+      wait @pid, streams, client
     rescue Exception => e
       log "exception: #{e}"
-      manager.puts unless pid
+      manager.puts unless @pid
 
       if streams && !e.is_a?(SystemExit)
         print_exception(stderr, e)
         streams.each(&:close)
       end
 
-      client.puts(1) if pid
+      client.puts(1) if @pid
       client.close
     end
 
diff --git a/test/acceptance/app_test.rb b/test/acceptance/app_test.rb
index 90896b06..2df00ee2 100644
--- a/test/acceptance/app_test.rb
+++ b/test/acceptance/app_test.rb
@@ -291,6 +291,18 @@ def binstub_prelude
     assert_success "bin/rake -p 'Rails.env'", stdout: "test"
   end
 
+  test "config via environment variable" do
+    File.write(app.path('config/initializers/set_foo.rb'), <<-CONFIG)
+      Rails.application.config.foo = !!ENV['FOO']
+    CONFIG
+
+    app.env['FOO'] = '1'
+    assert_success "bin/rails runner -e test 'p Rails.application.config.foo'", stdout: "true"
+
+    app.env['FOO'] = nil
+    assert_success "bin/rails runner -e development 'p Rails.application.config.foo'", stdout: "false"
+  end
+
   test "setting env vars with rake" do
     File.write(app.path("lib/tasks/env.rake"), <<-'CODE')
       task :print_rails_env => :environment do