diff --git a/release/tools/azure.conf b/release/tools/azure.conf
index 60076984b1bd..c88651a07745 100644
--- a/release/tools/azure.conf
+++ b/release/tools/azure.conf
@@ -6,7 +6,7 @@
 # Set to a list of packages to install.
 # Example:
 #export VM_EXTRA_PACKAGES="www/apache24"
-export VM_EXTRA_PACKAGES="sysutils/azure-agent"
+export VM_EXTRA_PACKAGES="${VM_EXTRA_PACKAGES} sysutils/azure-agent"
 
 # Set to a list of third-party software to enable in rc.conf(5).
 # Example:
diff --git a/release/tools/ec2.conf b/release/tools/ec2.conf
index 888a446659a5..2bf47b01077d 100644
--- a/release/tools/ec2.conf
+++ b/release/tools/ec2.conf
@@ -6,7 +6,9 @@
 # Packages to install into the image we're creating.  This is a deliberately
 # minimalist set, providing only the packages necessary to bootstrap further
 # package installation as specified via EC2 user-data.
-export VM_EXTRA_PACKAGES="ec2-scripts firstboot-freebsd-update firstboot-pkgs isc-dhcp44-client ebsnvme-id"
+export VM_EXTRA_PACKAGES="${VM_EXTRA_PACKAGES} ec2-scripts \
+	firstboot-freebsd-update firstboot-pkgs isc-dhcp44-client \
+	ebsnvme-id"
 
 # Include the amazon-ssm-agent package in amd64 images, since some users want
 # to be able to use it on systems which are not connected to the Internet.
diff --git a/release/tools/gce.conf b/release/tools/gce.conf
index 113784a7643e..745477f0bc8e 100644
--- a/release/tools/gce.conf
+++ b/release/tools/gce.conf
@@ -7,9 +7,10 @@
 export VMSIZE=20g
 
 # Set to a list of packages to install.
-export VM_EXTRA_PACKAGES="firstboot-freebsd-update firstboot-pkgs \
-	google-cloud-sdk panicmail sudo sysutils/py-google-compute-engine \
-	lang/python lang/python2 lang/python3"
+export VM_EXTRA_PACKAGES="${VM_EXTRA_PACKAGES} firstboot-freebsd-update \
+	firstboot-pkgs \ google-cloud-sdk panicmail sudo \
+	sysutils/py-google-compute-engine lang/python lang/python2 \
+	lang/python3"
 
 # Set to a list of third-party software to enable in rc.conf(5).
 export VM_RC_LIST="ntpd sshd growfs \
diff --git a/release/tools/vagrant.conf b/release/tools/vagrant.conf
index 05e7052d46c4..ebf69338b7d7 100644
--- a/release/tools/vagrant.conf
+++ b/release/tools/vagrant.conf
@@ -8,7 +8,8 @@ export VMSIZE=8g
 
 # Packages to install into the image we're creating.  This is a deliberately
 # minimalist set, providing only the packages necessary to bootstrap.
-export VM_EXTRA_PACKAGES="shells/bash firstboot-freebsd-update firstboot-pkgs"
+export VM_EXTRA_PACKAGES="${VM_EXTRA_PACKAGES} shells/bash \
+	firstboot-freebsd-update firstboot-pkgs"
 
 # Set to a list of third-party software to enable in rc.conf(5).
 export VM_RC_LIST="firstboot_freebsd_update firstboot_pkgs growfs"