diff --git a/setup.sh b/setup.sh
index bd8fedc..bf35bb6 100755
--- a/setup.sh
+++ b/setup.sh
@@ -11,6 +11,14 @@ source /root/.bash_profile
 # Load the cluster variables set by the deploy script
 source ec2-variables.sh
 
+function approve_ssh_keys () {
+  pssh --inline \
+      --host "localhost $(hostname) $MASTERS $SLAVES" \
+      --user root \
+      --extra-args "$SSH_OPTS" \
+      ":"
+}
+
 # Set hostname based on EC2 private DNS name, so that it is set correctly
 # even if the instance is restarted with a different private DNS name
 PRIVATE_DNS=`wget -q -O - http://instance-data.ec2.internal/latest/meta-data/local-hostname`
@@ -45,11 +53,7 @@ echo "Setting executable permissions on scripts..."
 find . -regex "^.+.\(sh\|py\)" | xargs chmod a+x
 
 echo "SSH-ing to all cluster nodes to approve keys..."
-pssh --inline \
-    --host "localhost $(hostname) $MASTERS $SLAVES" \
-    --user root \
-    --extra-args "$SSH_OPTS" \
-    ":"
+approve_ssh_keys
 
 echo "RSYNC'ing /root/spark-ec2 to other cluster nodes..."
 for node in $SLAVES $OTHER_MASTERS; do
@@ -67,6 +71,9 @@ pssh --inline \
     --extra-args "-t -t $SSH_OPTS" \
     "spark-ec2/setup-slave.sh"
 
+echo "SSH-ing to all cluster nodes to re-approve keys..."
+# We do this again because setup-slave.sh clears out .ssh/known_hosts.
+approve_ssh_keys
 
 # Always include 'scala' module if it's not defined as a work around
 # for older versions of the scripts.