From 9ec0ea6267311b66df94dd7b2eb978ac2eb44a0d Mon Sep 17 00:00:00 2001
From: Mark Harrah <dmharrah@gmail.com>
Date: Tue, 28 May 2013 07:56:48 -0400
Subject: [PATCH] Only add automatically detected plugins to options once. 
 Fixes #757.

---
 main/Defaults.scala | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/main/Defaults.scala b/main/Defaults.scala
index 9d5b74e7a..d4cd4795f 100755
--- a/main/Defaults.scala
+++ b/main/Defaults.scala
@@ -1179,7 +1179,9 @@ object Classpaths
 
 	lazy val compilerPluginConfig = Seq(
 		scalacOptions <<= (scalacOptions, autoCompilerPlugins, update) map { (options, auto, report) =>
-			if(auto) options ++ autoPlugins(report) else options
+			val newPlugins = autoPlugins(report)
+			val existing = options.toSet
+			if(auto) options ++ newPlugins.filterNot(existing) else options
 		}
 	)
 	def substituteScalaFiles(scalaInstance: ScalaInstance, report: UpdateReport): UpdateReport =