diff --git a/compile/ScalaInstance.scala b/compile/ScalaInstance.scala
index a0ab64fe5..3eae59b4f 100644
--- a/compile/ScalaInstance.scala
+++ b/compile/ScalaInstance.scala
@@ -9,8 +9,10 @@ package xsbt
 * The 'actualVersion' field should be used to uniquely identify the compiler.  It is obtained from the compiler.properties file.*/
 final class ScalaInstance(val version: String, val loader: ClassLoader, val libraryJar: File, val compilerJar: File) extends NotNull
 {
+	require(version.indexOf(' ') < 0, "Version cannot contain spaces (was '" + version + "')")
 	/** Gets the version of Scala in the compiler.properties file from the loader.  This version may be different than that given by 'version'*/
 	lazy val actualVersion = ScalaInstance.actualVersion(loader)(" version " + version)
+	override def toString = "Scala instance{version label " + version + ", actual version " + actualVersion + ", library jar: " + libraryJar + ", compiler jar: " + compilerJar + "}"
 }
 object ScalaInstance
 {