diff --git a/specs/core/0_beacon-chain.md b/specs/core/0_beacon-chain.md
index 3470459e1..bf210c60c 100644
--- a/specs/core/0_beacon-chain.md
+++ b/specs/core/0_beacon-chain.md
@@ -1216,19 +1216,15 @@ Let `genesis_block = BeaconBlock(state_root=hash_tree_root(genesis_state))`.
 
 ## Beacon chain state transition function
 
-The post-state corresponding to a pre-state `state` and a block `block` is defined as `state_transition(state, block)`.
+The post-state corresponding to a pre-state `state` and a block `block` is defined as `state_transition(state, block)`. State transitions that trigger an unhandled excpetion (e.g. a failed `assert` or an out-of-range list access) are considered invalid.
 
 ```python
 def state_transition(state: BeaconState, block: BeaconBlock) -> BeaconState:
-    pre_state = copy.deepcopy(state)
-    try:
-        # Process slots (including those with no blocks) since block
-        process_slots(state, block.slot)
-        # Process block
-        process_block(state, block)
-    except Exception:
-        # State is not advanced on exceptions (e.g. a failed `assert` or an out-of-range list access)
-        return pre_state
+    # Process slots (including those with no blocks) since block
+    process_slots(state, block.slot)
+    # Process block
+    process_block(state, block)
+    # Return post-state
     return state
 ```