diff --git a/specs/phase0/validator.md b/specs/phase0/validator.md
index 4576c4b90..cbe0c2d12 100644
--- a/specs/phase0/validator.md
+++ b/specs/phase0/validator.md
@@ -340,9 +340,10 @@ It is useful to be able to run a state transition function (working on a copy of
 
 ```python
 def compute_new_state_root(state: BeaconState, block: BeaconBlock) -> Root:
-    process_slots(state, block.slot)
-    process_block(state, block)
-    return hash_tree_root(state)
+    temp_state: BeaconState = state.copy()
+    signed_block = SignedBeaconBlock(message=block)
+    temp_state = state_transition(temp_state, signed_block, validate_result=False)
+    return hash_tree_root(temp_state)
 ```
 
 ##### Signature
diff --git a/tests/core/pyspec/eth2spec/test/validator/test_validator_unittest.py b/tests/core/pyspec/eth2spec/test/validator/test_validator_unittest.py
index a655cb486..5bb246ed5 100644
--- a/tests/core/pyspec/eth2spec/test/validator/test_validator_unittest.py
+++ b/tests/core/pyspec/eth2spec/test/validator/test_validator_unittest.py
@@ -246,6 +246,7 @@ def test_compute_new_state_root(spec, state):
     state_root = spec.compute_new_state_root(state, block)
 
     assert state_root != pre_state.hash_tree_root()
+    assert state == pre_state
 
     # dumb verification
     spec.process_slots(post_state, block.slot)