diff --git a/util/crossgcc/buildgcc b/util/crossgcc/buildgcc
index 12696c0df9..57eb5125a4 100755
--- a/util/crossgcc/buildgcc
+++ b/util/crossgcc/buildgcc
@@ -51,8 +51,8 @@ MAKE_VERSION=4.1
 # These are sanitized by the jenkins toolchain test builder, so if
 # a completely new URL is added here, it probably needs to be added
 # to the jenkins build as well, or the builder won't download it.
-GMP_ARCHIVE="http://ftpmirror.gnu.org/gmp/gmp-${GMP_VERSION}.tar.bz2"
-MPFR_ARCHIVE="http://ftpmirror.gnu.org/mpfr/mpfr-${MPFR_VERSION}.tar.bz2"
+GMP_ARCHIVE="http://ftpmirror.gnu.org/gmp/gmp-${GMP_VERSION}.tar.xz"
+MPFR_ARCHIVE="http://ftpmirror.gnu.org/mpfr/mpfr-${MPFR_VERSION}.tar.xz"
 MPC_ARCHIVE="http://ftpmirror.gnu.org/mpc/mpc-${MPC_VERSION}.tar.gz"
 LIBELF_ARCHIVE="http://www.mr511.de/software/libelf-${LIBELF_VERSION}.tar.gz"
 GCC_ARCHIVE="http://ftpmirror.gnu.org/gcc/gcc-${GCC_VERSION}/gcc-${GCC_VERSION}.tar.bz2"
diff --git a/util/crossgcc/sum/gmp-6.1.0.tar.bz2.cksum b/util/crossgcc/sum/gmp-6.1.0.tar.bz2.cksum
deleted file mode 100644
index 06db257b98..0000000000
--- a/util/crossgcc/sum/gmp-6.1.0.tar.bz2.cksum
+++ /dev/null
@@ -1 +0,0 @@
-db38c7b67f8eea9f2e5b8a48d219165b2fdab11f  tarballs/gmp-6.1.0.tar.bz2
diff --git a/util/crossgcc/sum/gmp-6.1.0.tar.xz.cksum b/util/crossgcc/sum/gmp-6.1.0.tar.xz.cksum
new file mode 100644
index 0000000000..348b80f7af
--- /dev/null
+++ b/util/crossgcc/sum/gmp-6.1.0.tar.xz.cksum
@@ -0,0 +1 @@
+99d691607613e749aa5d7c0c2a89aeab38fec070  tarballs/gmp-6.1.0.tar.xz
diff --git a/util/crossgcc/sum/mpfr-3.1.4.tar.xz.cksum b/util/crossgcc/sum/mpfr-3.1.4.tar.xz.cksum
new file mode 100644
index 0000000000..90f90ebb5d
--- /dev/null
+++ b/util/crossgcc/sum/mpfr-3.1.4.tar.xz.cksum
@@ -0,0 +1 @@
+cedc0055d55b6ee4cd17e1e6119ed412520ff81a  tarballs/mpfr-3.1.4.tar.xz