Index: ExternalProject.cmake
===================================================================
--- ExternalProject.cmake	(revision 12435)
+++ ExternalProject.cmake	(revision 12436)
@@ -504,7 +504,7 @@
 function(_ep_write_extractfile_script script_filename name filename directory)
   set(args "")
 
-  if(filename MATCHES "(\\.|=)(bz2|tar\\.gz|tgz|zip)$")
+  if(filename MATCHES "(\\.|=)(bz2|tar\\.gz|tar\\.xz|tgz|zip)$")
     set(args xfz)
   endif()
 
@@ -513,7 +513,7 @@
   endif()
 
   if(args STREQUAL "")
-    message(SEND_ERROR "error: do not know how to extract '${filename}' -- known types are .bz2, .tar, .tar.gz, .tgz and .zip")
+    message(SEND_ERROR "error: do not know how to extract '${filename}' -- known types are .bz2, .tar, .tar.gz, tar.xz, .tgz and .zip")
     return()
   endif()
 
@@ -1301,11 +1301,11 @@
         if("x${fname}" STREQUAL "x")
           string(REGEX MATCH "[^/\\?]*$" fname "${url}")
         endif()
-        if(NOT "${fname}" MATCHES "(\\.|=)(bz2|tar|tgz|tar\\.gz|zip)$")
-          string(REGEX MATCH "([^/\\?]+(\\.|=)(bz2|tar|tgz|tar\\.gz|zip))/.*$" match_result "${url}")
+        if(NOT "${fname}" MATCHES "(\\.|=)(bz2|tar|tgz|tar\\.gz|tar\\.xz|zip)$")
+          string(REGEX MATCH "([^/\\?]+(\\.|=)(bz2|tar|tgz|tar\\.gz|tar\\.xz|zip))/.*$" match_result "${url}")
           set(fname "${CMAKE_MATCH_1}")
         endif()
-        if(NOT "${fname}" MATCHES "(\\.|=)(bz2|tar|tgz|tar\\.gz|zip)$")
+        if(NOT "${fname}" MATCHES "(\\.|=)(bz2|tar|tgz|tar\\.gz|tar\\.xz|zip)$")
           message(FATAL_ERROR "Could not extract tarball filename from url:\n  ${url}")
         endif()
         string(REPLACE ";" "-" fname "${fname}")