diff --git a/regression-tests/Makefile.simulation-test b/regression-tests/Makefile.simulation-test
index 4af001ef0..466664f89 100644
--- a/regression-tests/Makefile.simulation-test
+++ b/regression-tests/Makefile.simulation-test
@@ -30,6 +30,8 @@ TESTS=$(wildcard ??-*.csc)
 TESTLOGS=$(patsubst %.csc,%.testlog,$(TESTS))
 LOGS=$(patsubst %.csc,%.log,$(TESTS))
 FAILLOGS=$(patsubst %.csc,%.faillog,$(TESTS))
+#Set random seed to create reproduceable results.
+RANDOMSEED=1
 
 CONTIKI=../..
 
@@ -57,7 +59,7 @@ endif
 %.testlog: %.csc cooja
 	@echo -n Running test $(basename $<) ... ""
 	@(java -Xshare:on -jar $(CONTIKI)/tools/cooja/dist/cooja.jar \
-              -nogui=$< -contiki=$(CONTIKI) > $(basename $@).log || \
+              -nogui=$< -contiki=$(CONTIKI) -random-seed=$(RANDOMSEED) > $(basename $@).log || \
          (echo " FAIL ಠ_ಠ" | tee -a COOJA.testlog; \
 	  tail -50 COOJA.log; \
           mv COOJA.testlog $(basename $<).faillog; \