diff --git a/Cargo.lock b/Cargo.lock
index 1e40a750f..c9da3375f 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -6372,6 +6372,24 @@ dependencies = [
  "tap",
 ]
 
+[[package]]
+name = "x509-parser"
+version = "0.14.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e0ecbeb7b67ce215e40e3cc7f2ff902f94a223acf44995934763467e7b1febc8"
+dependencies = [
+ "asn1-rs",
+ "base64 0.13.1",
+ "data-encoding",
+ "der-parser",
+ "lazy_static",
+ "nom",
+ "oid-registry",
+ "rusticata-macros",
+ "thiserror",
+ "time",
+]
+
 [[package]]
 name = "xattr"
 version = "1.3.1"
diff --git a/programs/manifest/src/state/market.rs b/programs/manifest/src/state/market.rs
index 8ee66d3de..2df515174 100644
--- a/programs/manifest/src/state/market.rs
+++ b/programs/manifest/src/state/market.rs
@@ -861,10 +861,8 @@ impl<Fixed: DerefOrBorrowMut<MarketFixed>, Dynamic: DerefOrBorrowMut<[u8]>>
             }
         }
 
-        // TODO: Remove the silent failures
-        // Silently fails because order could have matched before our cancel got
-        // there and that is correct behavior in that case.
-        Ok(())
+        // Do not fail silently.
+        Err(ManifestError::InvalidCancel.into())
     }
 
     pub fn cancel_order_by_index(
diff --git a/programs/manifest/tests/cases/cancel_order.rs b/programs/manifest/tests/cases/cancel_order.rs
index 9168451aa..7a3155d06 100644
--- a/programs/manifest/tests/cases/cancel_order.rs
+++ b/programs/manifest/tests/cases/cancel_order.rs
@@ -95,8 +95,8 @@ async fn cancel_order_sequence_number_not_exist_test() -> anyhow::Result<()> {
         .place_order(Side::Ask, 1, 1, 0, u32::MAX, OrderType::Limit)
         .await?;
 
-    // Sequence number does not exist, but it fails open.
-    test_fixture.cancel_order(1234).await?;
+    // Sequence number does not exist. It fails closed.
+    assert!(test_fixture.cancel_order(1234).await.is_err());
 
     Ok(())
 }