diff --git a/lib/cli.js b/lib/cli.js
index 55098049..9229b29a 100644
--- a/lib/cli.js
+++ b/lib/cli.js
@@ -32,7 +32,7 @@ program
     , Number
     , 7400)
   .option('--max-port <port>'
-    , 'maximum port number for worker use (total must be multiple of 3)'
+    , 'maximum port number for worker use'
     , Number
     , 7700)
   .option('--public-ip <ip>'
diff --git a/lib/roles/provider.js b/lib/roles/provider.js
index 52eeb9c5..b8c931ea 100644
--- a/lib/roles/provider.js
+++ b/lib/roles/provider.js
@@ -27,6 +27,10 @@ module.exports = function(options) {
   }
   var totalsTimer
 
+  // To make sure that we always bind the same type of service to the same
+  // port, we must ensure that we allocate ports in fixed groups.
+  var ports = options.ports.slice(0, -options.ports.length % 3)
+
   // Information about total devices
   var delayedTotals = (function() {
     function totals() {
@@ -261,8 +265,8 @@ module.exports = function(options) {
 
       // Spawn a device worker
       function spawn() {
-        var ports = options.ports.splice(0, 3)
-          , proc = options.fork(device, ports)
+        var allocatedPorts = ports.splice(0, 3)
+          , proc = options.fork(device, allocatedPorts)
           , resolver = Promise.defer()
 
         function exitListener(code, signal) {
@@ -323,7 +327,7 @@ module.exports = function(options) {
             proc.removeListener('message', messageListener)
 
             // Return used ports to the main pool
-            Array.prototype.push.apply(options.ports, ports)
+            Array.prototype.push.apply(ports, allocatedPorts)
 
             // Update lists
             _.pull(lists.ready, device.id)