diff --git a/tests/core/pyspec/eth2spec/test/phase0/block_processing/test_process_attester_slashing.py b/tests/core/pyspec/eth2spec/test/phase0/block_processing/test_process_attester_slashing.py
index 4a2c7d61d..940bc47fb 100644
--- a/tests/core/pyspec/eth2spec/test/phase0/block_processing/test_process_attester_slashing.py
+++ b/tests/core/pyspec/eth2spec/test/phase0/block_processing/test_process_attester_slashing.py
@@ -1,4 +1,4 @@
-import random
+from random import Random
 
 from eth2spec.test.context import (
     spec_state_test, expect_assertion_error, always_bls, with_all_phases,
@@ -152,9 +152,10 @@ def test_success_misc_balances(spec, state):
 @single_phase
 def test_success_with_effective_balance_disparity(spec, state):
     # Jitter balances to be different from effective balances
+    rng = Random(12345)
     for i in range(len(state.balances)):
         pre = int(state.balances[i])
-        state.balances[i] += random.randrange(max(pre - 5000, 0), pre + 5000)
+        state.balances[i] += rng.randrange(max(pre - 5000, 0), pre + 5000)
 
     attester_slashing = get_valid_attester_slashing(spec, state, signed_1=True, signed_2=True)