diff --git a/documentation/install.md b/documentation/install.md
index 94305621..1fb95fb4 100644
--- a/documentation/install.md
+++ b/documentation/install.md
@@ -33,6 +33,10 @@ When installing a new PE cluster using peadm, there are several different host p
 
 Supplying a combination of host parameters which does not match one of the supported architectures above will result in an unsupported architecture error.
 
+## Requirements
+
+* Puppet must not be installed on any of the target PE cluster hosts prior to beginning install.
+
 ## Usage
 
 ### Bolt 3 usage
diff --git a/tasks/agent_install.sh b/tasks/agent_install.sh
index 85c0156c..7856f5e1 100755
--- a/tasks/agent_install.sh
+++ b/tasks/agent_install.sh
@@ -2,6 +2,11 @@
 
 set -e
 
+if [ -x "/opt/puppetlabs/bin/puppet" ]; then
+  echo "ERROR: Puppet agent is already installed. Re-install, re-configuration, or upgrade not supported. Please uninstall the agent before running this task."
+  exit 1
+fi
+
 flags=$(echo $PT_install_flags | sed -e 's/^\["*//' -e 's/"*\]$//' -e 's/", *"/ /g')
 
 curl -k "https://${PT_server}:8140/packages/current/install.bash" | bash -s -- $flags