diff --git a/CHANGELOG.adoc b/CHANGELOG.adoc
index 50f9828..0e06a44 100644
--- a/CHANGELOG.adoc
+++ b/CHANGELOG.adoc
@@ -2,6 +2,15 @@
 
 === [Unreleased]
 
+==== Fixed — JCS numbers on decimal ties
+
+* `+ijson-jcs+` is bumped from 3a9a4ee to 03df9ed, which formats numbers with
+`+ryu-js+` (ECMAScript `+Number::toString+`). The old pin printed RFC 8785
+Appendix B vector 0x43143ff3c1cb0959 as `+1424953923781206.3+`; JCS requires
+`+1424953923781206.2+` (ties to even). Any report or attestation holding such a
+float now hashes to the value other JCS implementations compute. A test in
+`+crate::json+` pins the vector.
+
 ==== Fixed — KYAML keys holding a line separator
 
 * KYAML output now escapes U+2028 (LS) and U+2029 (PS) as `+\uXXXX+`, as it
diff --git a/Cargo.lock b/Cargo.lock
index d10e538..e223d5e 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2212,8 +2212,9 @@ dependencies = [
 [[package]]
 name = "ijson-jcs"
 version = "0.1.0"
-source = "git+https://github.com/hyperpolymath/ijson-jcs?rev=3a9a4ee326a968a32b2f152b4faec243a2d00765#3a9a4ee326a968a32b2f152b4faec243a2d00765"
+source = "git+https://github.com/hyperpolymath/ijson-jcs?rev=03df9ed20c1a2e1d6d913b8b20cf0874651bb61a#03df9ed20c1a2e1d6d913b8b20cf0874651bb61a"
 dependencies = [
+ "ryu-js",
  "serde",
  "serde_json",
  "thiserror 2.0.18",
@@ -3708,6 +3709,12 @@ dependencies = [
  "wait-timeout",
 ]
 
+[[package]]
+name = "ryu-js"
+version = "1.0.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "04d056b875a9d2e6cb9a61d127afee9ac5999b9f87bcb32079d1318e505be714"
+
 [[package]]
 name = "same-file"
 version = "1.0.6"
diff --git a/Cargo.toml b/Cargo.toml
index a412e58..f6c0545 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -27,7 +27,7 @@ serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
 # JCS (RFC 8785) for JSON artefacts: the estate tool behind JSON-POLICY rule
 # J-1. Not on crates.io, so pinned to a full commit SHA.
-ijson-jcs = { git = "https://github.com/hyperpolymath/ijson-jcs", rev = "3a9a4ee326a968a32b2f152b4faec243a2d00765" }
+ijson-jcs = { git = "https://github.com/hyperpolymath/ijson-jcs", rev = "03df9ed20c1a2e1d6d913b8b20cf0874651bb61a" }
 # Pure safe-Rust YAML (replaces serde_yaml + unsafe-libyaml, RUSTSEC-2024-0449).
 serde-saphyr = "2.0"
 regex = "1.10"
diff --git a/src/json.rs b/src/json.rs
index b6a7c2d..65eb5a4 100644
--- a/src/json.rs
+++ b/src/json.rs
@@ -61,6 +61,14 @@ mod tests {
         );
     }
 
+    #[test]
+    fn numbers_follow_rfc_8785_on_decimal_ties() {
+        // RFC 8785 Appendix B: binary64 0x43143ff3c1cb0959 must print as
+        // ECMAScript does, choosing the even digit on a decimal tie.
+        let tie = f64::from_bits(0x4314_3ff3_c1cb_0959);
+        assert_eq!(to_canonical_string(&tie).unwrap(), "1424953923781206.2\n");
+    }
+
     #[test]
     fn rejects_integers_outside_i_json_range() {
         // I-JSON safe integers: [-(2^53 - 1), 2^53 - 1].