diff --git a/tests/14-rpl-lite/07-rpl-random-rearrangement.csc b/tests/14-rpl-lite/07-rpl-random-rearrangement.csc
index cdb62c420..16ba26e20 100644
--- a/tests/14-rpl-lite/07-rpl-random-rearrangement.csc
+++ b/tests/14-rpl-lite/07-rpl-random-rearrangement.csc
@@ -544,7 +544,7 @@ make receiver-node.cooja TARGET=cooja</commands>
 }&#xD;
 &#xD;
 function getRandom(min, max) {&#xD;
-  return Math.random() * (max - min) + min;&#xD;
+  return r.nextFloat() * (max - min) + min;&#xD;
 }&#xD;
 &#xD;
 // From: http://bost.ocks.org/mike/shuffle/&#xD;
@@ -555,7 +555,7 @@ function shuffle(array) {&#xD;
   while (m) {&#xD;
 &#xD;
     // Pick a remaining element…&#xD;
-    i = Math.floor(Math.random() * m--);&#xD;
+    i = Math.floor(r.nextFloat() * m--);&#xD;
 &#xD;
     // And swap it with the current element.&#xD;
     t = array[m];&#xD;
@@ -571,6 +571,7 @@ GENERATE_MSG(1200000, 'randomize-nodes');&#xD;
 GENERATE_MSG(2400000, 'randomize-nodes');&#xD;
 GENERATE_MSG(3600000, 'randomize-nodes');&#xD;
 &#xD;
+var r = new java.util.Random(sim.getRandomSeed());&#xD;
 var numForwarders = 20;&#xD;
 var forwardIDStart = 4;&#xD;
 packetsReceived = [];&#xD;
diff --git a/tests/15-rpl-classic/07-rpl-random-rearrangement.csc b/tests/15-rpl-classic/07-rpl-random-rearrangement.csc
index cdb62c420..16ba26e20 100644
--- a/tests/15-rpl-classic/07-rpl-random-rearrangement.csc
+++ b/tests/15-rpl-classic/07-rpl-random-rearrangement.csc
@@ -544,7 +544,7 @@ make receiver-node.cooja TARGET=cooja</commands>
 }&#xD;
 &#xD;
 function getRandom(min, max) {&#xD;
-  return Math.random() * (max - min) + min;&#xD;
+  return r.nextFloat() * (max - min) + min;&#xD;
 }&#xD;
 &#xD;
 // From: http://bost.ocks.org/mike/shuffle/&#xD;
@@ -555,7 +555,7 @@ function shuffle(array) {&#xD;
   while (m) {&#xD;
 &#xD;
     // Pick a remaining element…&#xD;
-    i = Math.floor(Math.random() * m--);&#xD;
+    i = Math.floor(r.nextFloat() * m--);&#xD;
 &#xD;
     // And swap it with the current element.&#xD;
     t = array[m];&#xD;
@@ -571,6 +571,7 @@ GENERATE_MSG(1200000, 'randomize-nodes');&#xD;
 GENERATE_MSG(2400000, 'randomize-nodes');&#xD;
 GENERATE_MSG(3600000, 'randomize-nodes');&#xD;
 &#xD;
+var r = new java.util.Random(sim.getRandomSeed());&#xD;
 var numForwarders = 20;&#xD;
 var forwardIDStart = 4;&#xD;
 packetsReceived = [];&#xD;