diff --git a/Dockerfile b/Dockerfile
index 8ce295ae6aa..9554ec552d7 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -5,6 +5,12 @@ VOLUME /config
 
 RUN pip3 install --no-cache-dir -r requirements_all.txt
 
+# For the nmap tracker
+RUN apt-get update && \
+    apt-get install -y --no-install-recommends nmap net-tools && \
+    apt-get clean && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
+
+# Open Z-Wave disabled because broken
 #RUN apt-get update && \
 #    apt-get install -y cython3 libudev-dev && \
 #    apt-get clean && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/* && \
diff --git a/homeassistant/components/device_tracker/nmap_tracker.py b/homeassistant/components/device_tracker/nmap_tracker.py
index 8724f3a196a..7a795deae7b 100644
--- a/homeassistant/components/device_tracker/nmap_tracker.py
+++ b/homeassistant/components/device_tracker/nmap_tracker.py
@@ -137,9 +137,7 @@ class NmapDeviceScanner(object):
                 continue
             name = info['hostnames'][0] if info['hostnames'] else ipv4
             # Mac address only returned if nmap ran as root
-            mac = info['addresses'].get('mac')
-            if mac is None:
-                mac = _arp(ipv4)
+            mac = info['addresses'].get('mac') or _arp(ipv4)
             if mac is None:
                 continue
             device = Device(mac.upper(), name, ipv4, now)