diff --git a/linuxptp.spec b/linuxptp.spec
index f029078..b65f28c 100644
--- a/linuxptp.spec
+++ b/linuxptp.spec
@@ -61,6 +61,8 @@ echo '.so man8/timemaster.8' > $RPM_BUILD_ROOT%{_mandir}/man5/timemaster.conf.5
 
 %check
 cd testsuite
+# set random seed to get deterministic results
+export CLKNETSIM_RANDOM_SEED=26743
 make %{?_smp_mflags} -C clknetsim
 PATH=..:$PATH ./run