diff --git a/src/main/scala/scala/tools/partest/nest/AntRunner.scala b/src/main/scala/scala/tools/partest/nest/AntRunner.scala
index 12b4190..4800172 100644
--- a/src/main/scala/scala/tools/partest/nest/AntRunner.scala
+++ b/src/main/scala/scala/tools/partest/nest/AntRunner.scala
@@ -20,7 +20,7 @@ abstract class AntRunner(srcDir: String, testClassLoader: URLClassLoader, javaCm
   nestUI = nestUI,
   javaCmdPath = Option(javaCmd).map(_.getAbsolutePath) getOrElse PartestDefaults.javaCmd,
   javacCmdPath = Option(javacCmd).map(_.getAbsolutePath) getOrElse PartestDefaults.javacCmd,
-  scalacExtraArgs = scalacArgs,
+  scalacExtraArgs = scalacArgs.toIndexedSeq,
   javaOpts = javaOpts.map(_.mkString(" ")).getOrElse(PartestDefaults.javaOpts)) {
 
   def error(msg: String): Nothing = sys.error(msg)
diff --git a/src/main/scala/scala/tools/partest/nest/Runner.scala b/src/main/scala/scala/tools/partest/nest/Runner.scala
index 2987de2..7df0242 100644
--- a/src/main/scala/scala/tools/partest/nest/Runner.scala
+++ b/src/main/scala/scala/tools/partest/nest/Runner.scala
@@ -607,7 +607,7 @@ class Runner(val testFile: File, val suiteRunner: SuiteRunner, val nestUI: NestU
       ) ++ antOptions ++ args
     )
 
-    runCommand(cmd, output)
+    runCommand(cmd.toIndexedSeq, output)
   }
 
   def runAntTest(): (Boolean, LogContext) = {
@@ -619,7 +619,7 @@ class Runner(val testFile: File, val suiteRunner: SuiteRunner, val nestUI: NestU
       nestUI.verbose("ant "+args.mkString(" "))
 
       pushTranscript(s"ant ${args.mkString(" ")}")
-      nextTestActionExpectTrue("ant failed", ant(args, logFile)) && diffIsOk
+      nextTestActionExpectTrue("ant failed", ant(args.toIndexedSeq, logFile)) && diffIsOk
     }
     catch { // *catch-all*
       case e: Exception =>
diff --git a/src/main/scala/scala/tools/partest/sbt/SBTRunner.scala b/src/main/scala/scala/tools/partest/sbt/SBTRunner.scala
index 7735dde..b90ac45 100644
--- a/src/main/scala/scala/tools/partest/sbt/SBTRunner.scala
+++ b/src/main/scala/scala/tools/partest/sbt/SBTRunner.scala
@@ -64,7 +64,7 @@ class SBTRunner(val config: RunnerSpec.Config,
     nestUI = nestUI,
     javaCmdPath = Option(javaCmd).map(_.getAbsolutePath) getOrElse PartestDefaults.javaCmd,
     javacCmdPath = Option(javacCmd).map(_.getAbsolutePath) getOrElse PartestDefaults.javacCmd,
-    scalacExtraArgs = scalacArgs,
+    scalacExtraArgs = scalacArgs.toIndexedSeq,
     javaOpts = javaOpts,
     scalacOpts = scalacOpts) { self =>