diff --git a/CMakeLists.txt b/CMakeLists.txt
index 355230571..5ca11a594 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -736,8 +736,8 @@ if(NOT ARMADILLO_FOUND)
      message(STATUS " Armadillo will be downloaded and built automatically ")
      message(STATUS " when doing 'make'. ")
 
-     set(armadillo_RELEASE 6.200.4)
-     set(armadillo_MD5 "20c9de6ad06b4339a7fd3f67d78922e4")
+     set(armadillo_RELEASE 6.400.3)
+     set(armadillo_MD5 "b4c18561f080c710dc5bcd89533e68f8")
 
      ExternalProject_Add(
          armadillo-${armadillo_RELEASE}
diff --git a/README.md b/README.md
index 38c69d698..46c1d0564 100644
--- a/README.md
+++ b/README.md
@@ -94,9 +94,9 @@ In case you do not want to use PyBOMBS and prefer to build and install GNU Radio
 $ 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-6.200.4.tar.gz
-$ tar xvfz armadillo-6.200.4.tar.gz
-$ cd armadillo-6.200.4
+$ wget http://sourceforge.net/projects/arma/files/armadillo-6.400.3.tar.gz
+$ tar xvfz armadillo-6.400.3.tar.gz
+$ cd armadillo-6.400.3
 $ cmake .
 $ make
 $ sudo make install