diff --git a/server/Dockerfile b/server/Dockerfile
index d5ccdd2..f80321c 100644
--- a/server/Dockerfile
+++ b/server/Dockerfile
@@ -1,4 +1,4 @@
-FROM node
+FROM node:15.4.0
 WORKDIR /app
 
 COPY package*.json ./
diff --git a/server/src/lib/wifiDevices.js b/server/src/lib/wifiDevices.js
index 0b33bd6..ea574ba 100644
--- a/server/src/lib/wifiDevices.js
+++ b/server/src/lib/wifiDevices.js
@@ -62,7 +62,7 @@ async function forceUserDisconnect(mac) {
 
 function mockHostName({ mac, oui }) {
   const shortOui = oui ? oui.split(' ') : ''
-  const clearMac = mac?.replaceAll(':', '')
+  const clearMac = mac ? mac.replaceAll(':', '') : ''
 
   return `${shortOui}_${clearMac}`
 }
diff --git a/web/Dockerfile b/web/Dockerfile
index 37aea2d..365be47 100644
--- a/web/Dockerfile
+++ b/web/Dockerfile
@@ -1,5 +1,5 @@
 # build stage
-FROM node as build-stage
+FROM node:15.4.0 as build-stage
 WORKDIR /app
 COPY package*.json ./
 RUN npm install