diff --git a/CMakeLists.txt b/CMakeLists.txt
index ce0a953a2..7a275ad19 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -749,8 +749,8 @@ if(NOT ARMADILLO_FOUND)
          set(armadillo_MD5 "8116185e1d7391eed3bf6c500f81b4d8")
          set(ARMA_FILE_EXTENSION "gz")
      else(CMAKE_VERSION VERSION_LESS 3.1)
-         set(armadillo_RELEASE 7.200.2)
-         set(armadillo_MD5 "b21585372d67a8876117fd515d8cf0a2")
+         set(armadillo_RELEASE 7.400.1)
+         set(armadillo_MD5 "27fb0b62c02bf3f9ace1edd6e100dc78")
          set(ARMA_FILE_EXTENSION "xz")
      endif(CMAKE_VERSION VERSION_LESS 3.1)
 
diff --git a/README.md b/README.md
index 81cd93358..3e1de6d72 100644
--- a/README.md
+++ b/README.md
@@ -31,7 +31,7 @@ GNU/Linux
    * powerpc: the RISC 32-bit microprocessor architecture developed by IBM, Motorola (now Freescale) and Apple.
    * ppc64: 64-bit big-endian PowerPC architecture.
    * ppc64el: 64-bit little-endian PowerPC architecture.
-   * s390x: IBM's S/390 architecture for mainframes.
+   * s390x: IBM System z architecture for mainframe computers.
 
 Older distribution releases might work as well, but you will need GCC 4.7 or newer.
 
@@ -128,9 +128,9 @@ or manually as explained below, and then please follow instructions on how to [d
 $ sudo apt-get install libopenblas-dev liblapack-dev   # For Debian/Ubuntu/LinuxMint
 $ sudo yum install lapack-devel blas-devel             # For Fedora/CentOS/RHEL
 $ sudo zypper install lapack-devel blas-devel          # For OpenSUSE
-$ wget http://sourceforge.net/projects/arma/files/armadillo-7.200.2.tar.xz
-$ tar xvfz armadillo-7.200.2.tar.xz
-$ cd armadillo-7.200.2
+$ wget http://sourceforge.net/projects/arma/files/armadillo-7.400.1.tar.xz
+$ tar xvfz armadillo-7.400.1.tar.xz
+$ cd armadillo-7.400.1
 $ cmake .
 $ make
 $ sudo make install