diff --git a/Jenkinsfile b/Jenkinsfile
index af6b11561..ba5118aea 100644
--- a/Jenkinsfile
+++ b/Jenkinsfile
@@ -45,7 +45,12 @@ def runStages() {
 		}
 
 		stage("REST test suite") {
-			sh "./tests/simulation/restapi.sh --data-dir resttest0_data --base-port \$(( 9100 + EXECUTOR_NUMBER * 100 )) --base-rest-port \$(( 7100 + EXECUTOR_NUMBER * 100 )) --base-metrics-port \$(( 8108 + EXECUTOR_NUMBER * 100 )) --sleep-timeout 30"
+			sh """#!/bin/bash
+			set -e
+			./tests/simulation/restapi.sh --data-dir resttest0_data --base-port \$(( 9100 + EXECUTOR_NUMBER * 100 )) \
+				--base-rest-port \$(( 7100 + EXECUTOR_NUMBER * 100 )) --base-metrics-port \
+				\$(( 8108 + EXECUTOR_NUMBER * 100 )) --sleep-timeout 30 --kill-old-processes
+			"""
 		}
 
 		stage("Testnet finalization") {
diff --git a/scripts/launch_local_testnet.sh b/scripts/launch_local_testnet.sh
index aff1cd65e..60e980c34 100755
--- a/scripts/launch_local_testnet.sh
+++ b/scripts/launch_local_testnet.sh
@@ -315,6 +315,12 @@ cleanup() {
   sleep 2
   pkill -f -9 -P $$ nimbus_beacon_node &>/dev/null || true
   pkill -f -9 -P $$ nimbus_validator_client &>/dev/null || true
+
+  # Delete the binaries we just built, because these are unusable outside this
+  # local testnet.
+  for BINARY in ${BINARIES}; do
+    rm build/${BINARY}
+  done
 }
 trap 'cleanup' SIGINT SIGTERM EXIT
 
diff --git a/tests/simulation/restapi.sh b/tests/simulation/restapi.sh
index 4b0c2f49b..5c0ce5f3a 100755
--- a/tests/simulation/restapi.sh
+++ b/tests/simulation/restapi.sh
@@ -8,6 +8,7 @@ BASE_METRICS_PORT="48008"
 BASE_REST_PORT="47000"
 TIMEOUT_DURATION="30"
 TEST_DIRNAME="resttest0_data"
+KILL_OLD_PROCESSES="0"
 
 ####################
 # argument parsing #
@@ -27,7 +28,7 @@ if [ ${PIPESTATUS[0]} != 4 ]; then
 fi
 
 OPTS="h"
-LONGOPTS="help,data-dir:,base-port:,base-rest-port:,base-metrics-port:,sleep-timeout:"
+LONGOPTS="help,data-dir:,base-port:,base-rest-port:,base-metrics-port:,sleep-timeout:,kill-old-processes"
 
 print_help() {
   cat <<EOF
@@ -39,6 +40,7 @@ Usage: $(basename "$0") [OPTIONS] -- [BEACON NODE OPTIONS]
   --base-rest-port            bootstrap node's REST port (default: ${BASE_REST_PORT})
   --base-metrics-port         bootstrap node's metrics server port (default: ${BASE_METRICS_PORT})
   --sleep-timeout             timeout in seconds (default: ${TIMEOUT_DURATION} seconds)
+  --kill-old-processes        if any process is found listening on a port we use, kill it (default: disabled)
 EOF
 }
 
@@ -76,6 +78,10 @@ while true; do
       TIMEOUT_DURATION="$2"
       shift 2
       ;;
+    --kill-old-processes)
+      KILL_OLD_PROCESSES="1"
+      shift
+      ;;
     --)
       shift
       break
@@ -88,7 +94,6 @@ while true; do
 done
 
 NUM_VALIDATORS=${VALIDATORS:-32}
-TOTAL_NODES=${NODES:-1}
 GIT_ROOT="$(git rev-parse --show-toplevel)"
 TEST_DIR="${TEST_DIRNAME}"
 LOG_NODE_FILE="${TEST_DIR}/node_log.txt"
@@ -124,6 +129,21 @@ else
   NPROC="$(nproc)"
 fi
 
+# kill lingering processes from a previous run
+which lsof &>/dev/null || { echo "'lsof' not installed. Aborting."; exit 1; }
+for PORT in ${BASE_PORT} ${BASE_METRICS_PORT} ${BASE_REST_PORT}; do
+  for PID in $(lsof -n -i tcp:${PORT} -sTCP:LISTEN -t); do
+    echo -n "Found old process listening on port ${PORT}, with PID ${PID}. "
+    if [[ "${KILL_OLD_PROCESSES}" == "1" ]]; then
+      echo "Killing it."
+      kill -9 ${PID} || true
+    else
+      echo "Aborting."
+      exit 1
+    fi
+  done
+done
+
 build_if_missing () {
   if [[ ! -e "${GIT_ROOT}/build/${1}" ]]; then
     ${MAKE} -C "${GIT_ROOT}" -j ${NPROC} ${1}