diff --git a/crates/blockchain/state_transition/tests/stf_spectests.rs b/crates/blockchain/state_transition/tests/stf_spectests.rs
index 8a92fd4e..458cc2c0 100644
--- a/crates/blockchain/state_transition/tests/stf_spectests.rs
+++ b/crates/blockchain/state_transition/tests/stf_spectests.rs
@@ -53,6 +53,20 @@ fn run(path: &Path) -> datatest_stable::Result<()> {
         match (result, test.post) {
             (Ok(_), Some(expected_post)) => {
                 compare_post_states(&post_state, &expected_post, &block_registry)?;
+                // Hardening: the full post-state hash_tree_root must equal the
+                // fixture's `postStateRoot`. The per-field `post` checks only
+                // pin the fields the fixture chose to enumerate; this catches
+                // any state field they omit.
+                if let Some(expected_root) = test.post_state_root {
+                    let actual_root = post_state.hash_tree_root();
+                    if actual_root != expected_root {
+                        return Err(format!(
+                            "Test '{name}' post-state root mismatch: \
+                             expected {expected_root:?}, got {actual_root:?}"
+                        )
+                        .into());
+                    }
+                }
             }
             (Ok(_), None) => {
                 return Err(
diff --git a/crates/blockchain/state_transition/tests/types.rs b/crates/blockchain/state_transition/tests/types.rs
index 0e766a69..262785b0 100644
--- a/crates/blockchain/state_transition/tests/types.rs
+++ b/crates/blockchain/state_transition/tests/types.rs
@@ -33,11 +33,10 @@ pub struct StateTransitionTest {
     pub pre: TestState,
     pub blocks: Vec<Block>,
     pub post: Option<PostState>,
-    /// Expected post-state `hash_tree_root`, present alongside `post`. Captured
-    /// only so `deny_unknown_fields` accepts it; the per-field `post` checks
-    /// already pin the post-state.
+    /// Expected post-state `hash_tree_root`, present alongside `post`. Asserted
+    /// against the full post-state root after the per-field `post` checks, so
+    /// any state field those checks don't enumerate is still pinned.
     #[serde(rename = "postStateRoot")]
-    #[allow(dead_code)]
     pub post_state_root: Option<H256>,
     /// Expected rejection reason for negative cases. Captured only so
     /// `deny_unknown_fields` accepts it; failure is asserted via a missing