diff --git a/util/io/IO.scala b/util/io/IO.scala
index 3a99b49e6..68f3030a3 100644
--- a/util/io/IO.scala
+++ b/util/io/IO.scala
@@ -525,11 +525,21 @@ object IO
 
 	def copyFile(sourceFile: File, targetFile: File, preserveLastModified: Boolean = false)
 	{
+		// NOTE: when modifying this code, test with larger values of CopySpec.MaxFileSizeBits than default
+
 		require(sourceFile.exists, "Source file '" + sourceFile.getAbsolutePath + "' does not exist.")
 		require(!sourceFile.isDirectory, "Source file '" + sourceFile.getAbsolutePath + "' is a directory.")
 		fileInputChannel(sourceFile) { in =>
 			fileOutputChannel(targetFile) { out =>
-				val copied = out.transferFrom(in, 0, in.size)
+				// maximum bytes per transfer according to  from http://dzone.com/snippets/java-filecopy-using-nio
+				val max = (64 * 1024 * 1024) - (32 * 1024)
+				val total = in.size
+				def loop(offset: Long): Long =
+					if(offset < total)
+						loop( offset + out.transferFrom(in, offset, max) )
+					else
+						offset
+				val copied = loop(0)
 				if(copied != in.size)
 					error("Could not copy '" + sourceFile + "' to '" + targetFile + "' (" + copied + "/" + in.size + " bytes copied)")
 			}
diff --git a/util/io/src/test/scala/CopySpec.scala b/util/io/src/test/scala/CopySpec.scala
new file mode 100644
index 000000000..6cdf5eaf3
--- /dev/null
+++ b/util/io/src/test/scala/CopySpec.scala
@@ -0,0 +1,70 @@
+package sbt
+
+import java.io.File
+import java.util.Arrays
+import org.scalacheck._
+import Prop._
+import Arbitrary.arbLong
+
+object CopySpec extends Properties("Copy")
+{
+	// set to 0.25 GB by default for success on most systems without running out of space.
+	// when modifying IO.copyFile, verify against 1 GB or higher, preferably > 4 GB
+	final val MaxFileSizeBits = 28
+	final val BufferSize = 1*1024*1024
+
+	val randomSize = Gen.choose(0, MaxFileSizeBits).map( 1L << _ )
+	val pow2Size = (0 to (MaxFileSizeBits - 1)).toList.map( 1L << _ )
+	val derivedSize = pow2Size.map(_ - 1) ::: pow2Size.map(_ + 1) ::: pow2Size
+
+	val fileSizeGen: Gen[Long] =
+		Gen.frequency(
+			80 -> Gen.oneOf(derivedSize),
+			8 -> randomSize,
+			1 -> Gen.value(0) 
+		)
+
+	property("same contents") = forAll(fileSizeGen, arbLong.arbitrary) { (size: Long, seed: Long) =>
+		IO.withTemporaryDirectory { dir =>
+			val f1 = new File(dir, "source")
+			val f2 = new File(dir, "dest")
+			generate(seed = seed, size = size, file = f1)
+			IO.copyFile(f1, f2)
+			checkContentsSame(f1, f2)
+			true
+		}
+	}
+
+	def generate(seed: Long, size: Long, file: File) {
+		val rnd = new java.util.Random(seed)
+		
+		val buffer = new Array[Byte](BufferSize)
+		def loop(offset: Long) {
+			val len = math.min(size - offset, BufferSize)
+			if(len > 0) {
+				rnd.nextBytes(buffer)
+				IO.append(file, buffer)
+				loop(offset + len)
+			}
+		}
+		if(size == 0L) IO.touch(file) else loop(0)
+	}
+	def checkContentsSame(f1: File, f2: File) {
+		val len = f1.length
+		assert(len == f2.length, "File lengths differ: " + (len, f2.length).toString + " for " + (f1, f2).toString)
+		Using.fileInputStream(f1) { in1 =>
+			Using.fileInputStream(f2) { in2 =>
+				val buffer1 = new Array[Byte](BufferSize)
+				val buffer2 = new Array[Byte](BufferSize)
+				def loop(offset: Long): Unit = if(offset < len) {
+					val read1 = in1.read(buffer1)
+					val read2 = in2.read(buffer2)
+					assert(read1 == read2, "Read " + (read1, read2).toString + " bytes from " + (f1, f2).toString)
+					assert(Arrays.equals(buffer1, buffer2), "Contents differed.")
+					loop(offset + read1)
+				}
+				loop(0)
+			}
+		}
+	}
+}
\ No newline at end of file