diff --git a/builder/package.centos-6 b/builder/package.centos-6
index 6fcaa90..beb371b 100644
--- a/builder/package.centos-6
+++ b/builder/package.centos-6
@@ -1,3 +1,5 @@
+#!/bin/bash
+
 if [[ ! -d /tmp/output/centos-6 ]]; then
   mkdir -p /tmp/output/centos-6
 fi
@@ -20,11 +22,14 @@ export PATH=/usr/local/rvm/rubies/ruby-2.6.3/bin/:/.gems/bin:${PATH}
 export GEM_HOME=/.gems
 export GEM_PATH=/.gems
 
-# Additional config for c++11 support
+# Additional config for C++11 support in R 3.6.
+# R 3.6.0 no longer sets CXX11 flags without a full C++11 compiler present, but
+# the default gcc 4.4.7 still partially supports C++11 through -std=gnu++0x.
+# Use the same CXX11 flags as the defaults in R versions prior to 3.6.0.
 sed -i 's/^CXX11\ =\ .*/CXX11\ =\ g++/g' /opt/R/${R_VERSION}/lib/R/etc/Makeconf
 sed -i 's/^CXX11FLAGS\ =\ .*/CXX11FLAGS\ =\ -g\ -O2\ \$\(LTO\)/g' /opt/R/${R_VERSION}/lib/R/etc/Makeconf
 sed -i 's/^CXX11PICFLAGS\ =\ .*/CXX11PICFLAGS\ =\ -fpic/g' /opt/R/${R_VERSION}/lib/R/etc/Makeconf
-sed -i 's/^CXX11STD\ =\ .*/CXX11STD\ =\ -std=gnu++11/g' /opt/R/${R_VERSION}/lib/R/etc/Makeconf
+sed -i 's/^CXX11STD\ =\ .*/CXX11STD\ =\ -std=gnu++0x/g' /opt/R/${R_VERSION}/lib/R/etc/Makeconf
 
 fpm \
   -s dir \
diff --git a/builder/package.centos-7 b/builder/package.centos-7
index 76b2ee2..e35430d 100644
--- a/builder/package.centos-7
+++ b/builder/package.centos-7
@@ -1,3 +1,5 @@
+#!/bin/bash
+
 if [[ ! -d /tmp/output/centos-7 ]]; then
   mkdir -p /tmp/output/centos-7
 fi
diff --git a/builder/package.debian-9 b/builder/package.debian-9
index 6780327..620dd48 100644
--- a/builder/package.debian-9
+++ b/builder/package.debian-9
@@ -1,3 +1,5 @@
+#!/bin/bash
+
 if [[ ! -d /tmp/output/debian-9 ]]; then
   mkdir -p /tmp/output/debian-9
 fi
diff --git a/builder/package.opensuse-15 b/builder/package.opensuse-15
index 58e14ff..83a3ecf 100644
--- a/builder/package.opensuse-15
+++ b/builder/package.opensuse-15
@@ -1,3 +1,5 @@
+#!/bin/bash
+
 if [[ ! -d /tmp/output/opensuse-15 ]]; then
   mkdir -p /tmp/output/opensuse-15
 fi
diff --git a/builder/package.opensuse-42 b/builder/package.opensuse-42
index 4cc1837..714b8bb 100644
--- a/builder/package.opensuse-42
+++ b/builder/package.opensuse-42
@@ -1,3 +1,5 @@
+#!/bin/bash
+
 if [[ ! -d /tmp/output/opensuse-42 ]]; then
   mkdir -p /tmp/output/opensuse-42
 fi
diff --git a/builder/package.ubuntu-1604 b/builder/package.ubuntu-1604
index 33aa081..fc5b187 100644
--- a/builder/package.ubuntu-1604
+++ b/builder/package.ubuntu-1604
@@ -1,3 +1,5 @@
+#!/bin/bash
+
 if [[ ! -d /tmp/output/ubuntu-1604 ]]; then
   mkdir -p /tmp/output/ubuntu-1604
 fi
diff --git a/builder/package.ubuntu-1804 b/builder/package.ubuntu-1804
index 2b3f7c4..a1ac4de 100644
--- a/builder/package.ubuntu-1804
+++ b/builder/package.ubuntu-1804
@@ -1,3 +1,5 @@
+#!/bin/bash
+
 if [[ ! -d /tmp/output/ubuntu-1804 ]]; then
   mkdir -p /tmp/output/ubuntu-1804
 fi