diff --git a/build/build.xml b/build/build.xml
index a7ae990..050a555 100644
--- a/build/build.xml
+++ b/build/build.xml
@@ -173,8 +173,8 @@
         <condition property="java.not.ok" value="true">
             <not>
                 <or>
-                    <contains string="${ant.java.version}" substring="1.5"/>
-                    <contains string="${ant.java.version}" substring="1.6"/>
+                    <contains string="${ant.java.version}" substring="1.7"/>
+                    <contains string="${ant.java.version}" substring="1.8"/>
                 </or>
             </not>
         </condition>
@@ -213,8 +213,9 @@
             destdir="${compile.dir}"
             includeAntRuntime="no"
             debug="on"
-            source="1.5"
-            target="1.5"
+            source="1.7"
+            target="1.7"
+            encoding="UTF-8"
             >
             <src path="${src.java.dir}"/>
             <patternset refid="compile.sources"/>
diff --git a/src/java/org/jivesoftware/multiplexer/Session.java b/src/java/org/jivesoftware/multiplexer/Session.java
index c50dae8..7307ac1 100644
--- a/src/java/org/jivesoftware/multiplexer/Session.java
+++ b/src/java/org/jivesoftware/multiplexer/Session.java
@@ -90,6 +90,7 @@
     }
 
     public static void removeSession(String streamID) {
+        StreamIDFactory.releaseId(streamID);
         sessions.remove(streamID);
     }
 
diff --git a/src/java/org/jivesoftware/multiplexer/StreamIDFactory.java b/src/java/org/jivesoftware/multiplexer/StreamIDFactory.java
index fb9eb8c..2e3da60 100644
--- a/src/java/org/jivesoftware/multiplexer/StreamIDFactory.java
+++ b/src/java/org/jivesoftware/multiplexer/StreamIDFactory.java
@@ -21,6 +21,8 @@
 package org.jivesoftware.multiplexer;
 
 import java.util.Random;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ThreadLocalRandom;
 
 /**
  * A basic stream ID factory that produces id's using java.util.Random
@@ -32,15 +34,21 @@
  * @author Gaston Dombiak
  */
 public class StreamIDFactory {
-    /**
-     * The random number to use, someone with Java can predict stream IDs if they can guess the current seed *
-     */
-    Random random = new Random();
+
+    private static final ConcurrentHashMap<String, Boolean> usingStreamIDs = new ConcurrentHashMap<>();
 
     String managerName = ConnectionManager.getInstance().getName();
 
     public String createStreamID() {
-        return managerName + Integer.toHexString(random.nextInt());
+        String streamID;
+        do {
+            streamID = managerName + Integer.toHexString(ThreadLocalRandom.current().nextInt());
+        } while(usingStreamIDs.putIfAbsent(streamID, Boolean.TRUE) == null);
+        return streamID;
+    }
+
+    public static void releaseId(String streamId){
+        usingStreamIDs.remove(streamId);
     }
 
 }