diff --git a/Dockerfile.mri.erb b/Dockerfile.mri.erb
index 5350b51f..db82e689 100644
--- a/Dockerfile.mri.erb
+++ b/Dockerfile.mri.erb
@@ -23,11 +23,13 @@ RUN rm -f /usr/local/bin/sudo && \
     echo "%sudo  ALL=(ALL)       ALL" >> /etc/sudoers
 <% else %>
 ENV DEBIAN_FRONTEND noninteractive
-RUN dpkg --add-architecture <%= foreign_dpkg_arch %> && \
-    apt-get -y update && \
-    apt-get install -y sudo wget autoconf cmake curl git-core pkg-config build-essential xz-utils unzip gnupg2 dirmngr && \
-    apt-get install -y zlib1g-dev:<%= foreign_dpkg_arch %> libreadline-dev:<%= foreign_dpkg_arch %> libsqlite0-dev:<%= foreign_dpkg_arch %> libssl-dev:<%= foreign_dpkg_arch %> libyaml-dev:<%= foreign_dpkg_arch %> libffi-dev:<%= foreign_dpkg_arch %> && \
-    rm -rf /var/lib/apt/lists/*
+COPY ./build/setup_dpkg_multiarch_for_target.sh /
+RUN /setup_dpkg_multiarch_for_target.sh <%= foreign_dpkg_arch %>;
+
+RUN apt-get -y -qq update && \
+    apt-get -y -qq install sudo wget autoconf cmake curl git-core pkg-config build-essential xz-utils unzip gnupg2 dirmngr && \
+    apt-get -y -qq install zlib1g-dev:<%= foreign_dpkg_arch %> libreadline-dev:<%= foreign_dpkg_arch %> libsqlite0-dev:<%= foreign_dpkg_arch %> libssl-dev:<%= foreign_dpkg_arch %> libyaml-dev:<%= foreign_dpkg_arch %> libffi-dev:<%= foreign_dpkg_arch %> && \
+    rm -rf /var/lib/apt/lists/*;
 <% end %>
 
 # Add "rvm" as system group, to avoid conflicts with host GIDs typically starting with 1000
@@ -92,7 +94,6 @@ RUN apt-get -y update && \
     apt-get install -y <%
 if platform=~/darwin/        %> clang python lzma-dev libxml2-dev libssl-dev libc++-10-dev <% end %><%
 if platform=~/aarch64-linux/ %> gcc-aarch64-linux-gnu g++-aarch64-linux-gnu <% end %><%
-if platform=~/x86_64-linux/        %> gcc-x86-64-linux-gnu g++-x86-64-linux-gnu <% end %><%
 if platform=~/arm-linux/     %> gcc-arm-linux-gnueabihf g++-arm-linux-gnueabihf <% end %><%
 if platform=~/x86-mingw32/   %> gcc-mingw-w64-i686 g++-mingw-w64-i686 <% end %><%
 if platform=~/x64-mingw32/   %> gcc-mingw-w64-x86-64 g++-mingw-w64-x86-64 <% end %> && \
diff --git a/build/setup_dpkg_multiarch_for_target.sh b/build/setup_dpkg_multiarch_for_target.sh
new file mode 100755
index 00000000..657899cf
--- /dev/null
+++ b/build/setup_dpkg_multiarch_for_target.sh
@@ -0,0 +1,43 @@
+#!/bin/bash
+
+set -exuo pipefail
+IFS=$'\n\t'
+
+main() {
+  local to_uninstall=()
+
+  if ! command -v dpkg-architecture; then
+    echo "dpkg-architecture not found, installing" >&2
+    apt-get -qq -y update
+    apt-get -qq -y install --no-install-recommends debhelper lsb-release
+    rm -rf /var/lib/apt/lists/*
+    to_uninstall+=("debhelper" "lsb-release")
+  fi
+
+  deb_host_arch="$(dpkg-architecture --query DEB_HOST_ARCH)"
+  deb_target_arch="$1"
+
+  if [ "$deb_target_arch" != "$deb_host_arch" ]; then
+    echo "Setting up multiarch support for $deb_target_arch" >&2
+
+    # Add arch support for target so we can install libs
+    dpkg --add-architecture "$deb_target_arch"
+    # Qualify our current source lists to make sure debian doesn't infer stuff
+    sed -i "s/^deb http/deb [arch=$deb_host_arch] http/" /etc/apt/sources.list
+    # Add sources for ported target libs
+    sh -c "echo \"deb [arch=$deb_target_arch] http://ports.ubuntu.com/ubuntu-ports $(lsb_release -cs) main universe restricted multiverse\" >> /etc/apt/sources.list"
+    sh -c "echo \"deb [arch=$deb_target_arch] http://ports.ubuntu.com/ubuntu-ports $(lsb_release -cs)-updates main universe restricted multiverse\" >> /etc/apt/sources.list"
+    sh -c "echo \"deb [arch=$deb_target_arch] http://ports.ubuntu.com/ubuntu-ports $(lsb_release -cs)-security main universe restricted multiverse\" >> /etc/apt/sources.list"
+    apt-get update
+  else
+    echo "No need to set up multiarch support for $deb_target_arch"
+  fi
+
+  if [ "${#to_uninstall[@]}" -gt 0 ]; then
+    apt-get remove -y "${to_uninstall[@]}"
+  fi
+
+  rm "$0"
+}
+
+main "$@"