diff --git a/launch/src/main/scala/xsbt/boot/Configuration.scala b/launch/src/main/scala/xsbt/boot/Configuration.scala
index 651d80033..e9464406a 100644
--- a/launch/src/main/scala/xsbt/boot/Configuration.scala
+++ b/launch/src/main/scala/xsbt/boot/Configuration.scala
@@ -126,8 +126,11 @@ object Configuration
 	}
 	// single-arg constructor doesn't properly escape
 	def filePathURI(path: String): URI = {
-		val f = new File(path)
-		new URI(if(f.isAbsolute) "file" else null, path, null)
+		if(path.startsWith("file:")) new URI(path)
+		else {
+			val f = new File(path)
+			new URI(if(f.isAbsolute) "file" else null, path, null)
+		}
 	}
 	def directoryURI(dir: File): URI = directoryURI(dir.toURI)
 	def directoryURI(uri: URI): URI = 
diff --git a/launch/src/test/scala/URITests.scala b/launch/src/test/scala/URITests.scala
index 75a91e6ed..42c2dc2bd 100644
--- a/launch/src/test/scala/URITests.scala
+++ b/launch/src/test/scala/URITests.scala
@@ -40,4 +40,20 @@ object URITests extends Properties("URI Tests")
 		s"via file: $viaFile" |:
 		(viaPath == viaFile)
 	}
+
+	property("filePathURI supports URIs") =  secure {
+		val s = "file:///is/a/uri/with%20spaces"
+		val decoded = "/is/a/uri/with spaces"
+		val encoded = "/is/a/uri/with%20spaces"
+		val fpURI = filePathURI(s)
+		val directURI = new URI(s)
+		s"filePathURI: $fpURI" |:
+		s"direct URI: $directURI" |:
+		s"getPath: ${fpURI.getPath}" |:
+		s"getRawPath: ${fpURI.getRawPath}" |:
+		(fpURI == directURI) &&
+		(fpURI.getPath == decoded) &&
+		(fpURI.getRawPath == encoded)
+	}
+
 }
\ No newline at end of file
diff --git a/src/sphinx/Detailed-Topics/Command-Line-Reference.rst b/src/sphinx/Detailed-Topics/Command-Line-Reference.rst
index 2c88478a0..26390e8b4 100644
--- a/src/sphinx/Detailed-Topics/Command-Line-Reference.rst
+++ b/src/sphinx/Detailed-Topics/Command-Line-Reference.rst
@@ -210,7 +210,11 @@ influence SBT execution. Also see :doc:`Launcher`.
 | `sbt.version`                | Version   | 0.11.3              | sbt version to use, usually taken from             | 
 |                              |           |                     | project/build.properties                           |
 +------------------------------+-----------+---------------------+----------------------------------------------------+
-| `sbt.boot.properties`        | File      |                     |                                                    |
+| `sbt.boot.properties`        | File      |                     | The path to find the SBT boot properties file.     |
+|                              |           |                     | This can be a relative path, relative to the SBT   |
+|                              |           |                     | base directory, the users home directory or the    |
+|                              |           |                     | location of the sbt jar file, or it can be an      |
+|                              |           |                     | absolute path, or it can be an absolute file URI.  |
 +------------------------------+-----------+---------------------+----------------------------------------------------+
 | `sbt.override.build.repos`   | Boolean   | false               | If true, repositories configured in a build        | 
 |                              |           |                     | definition are ignored and the repositories        |
diff --git a/src/sphinx/Detailed-Topics/Launcher.rst b/src/sphinx/Detailed-Topics/Launcher.rst
index cdc4d987a..6573f2348 100644
--- a/src/sphinx/Detailed-Topics/Launcher.rst
+++ b/src/sphinx/Detailed-Topics/Launcher.rst
@@ -57,13 +57,14 @@ increasing order of precedence:
 -  Put a configuration file named `sbt.boot.properties` on the
    classpath. Put it in the classpath root without the `/sbt` prefix.
 -  Specify the location of an alternate configuration on the command
-   line. This can be done by either specifying the location as the
-   system property `sbt.boot.properties` or as the first argument to
-   the launcher prefixed by `'@'`. The system property has lower
-   precedence. Resolution of a relative path is first attempted against
-   the current working directory, then against the user's home
-   directory, and then against the directory containing the launcher
-   jar. An error is generated if none of these attempts succeed.
+   line, either as a path or an absolute URI. This can be done by
+   either specifying the location as the system property
+   `sbt.boot.properties` or as the first argument to the launcher
+   prefixed by `'@'`. The system property has lower precedence.
+   Resolution of a relative path is first attempted against the current
+   working directory, then against the user's home directory, and then
+   against the directory containing the launcher jar. An error is
+   generated if none of these attempts succeed.
 
 Syntax
 ~~~~~~