diff --git a/.clippy.toml b/.clippy.toml
index 81d631e..f631664 100644
--- a/.clippy.toml
+++ b/.clippy.toml
@@ -1,4 +1,4 @@
-msrv = "1.72"  # MSRV
+msrv = "1.73"  # MSRV
 warn-on-all-wildcard-imports = true
 allow-expect-in-tests = true
 allow-unwrap-in-tests = true
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 8acac71..e962915 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -49,7 +49,7 @@ jobs:
     - name: No-default features
       run: cargo test --workspace --no-default-features
   msrv:
-    name: "Check MSRV: 1.72"
+    name: "Check MSRV: 1.73"
     runs-on: ubuntu-latest
     steps:
     - name: Checkout repository
@@ -57,7 +57,7 @@ jobs:
     - name: Install Rust
       uses: dtolnay/rust-toolchain@stable
       with:
-        toolchain: "1.72"  # MSRV
+        toolchain: "1.73"  # MSRV
     - uses: Swatinem/rust-cache@v2
     - name: Default features
       run: cargo check --workspace --all-targets
@@ -119,7 +119,7 @@ jobs:
     - name: Install Rust
       uses: dtolnay/rust-toolchain@stable
       with:
-        toolchain: "1.72"  # MSRV
+        toolchain: "1.73"  # MSRV
         components: clippy
     - uses: Swatinem/rust-cache@v2
     - name: Install SARIF tools
diff --git a/Cargo.toml b/Cargo.toml
index c2ea6e3..5904547 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -11,7 +11,7 @@ categories = ["development-tools::build-utils"]
 keywords = ["cargo", "packaging"]
 license = "MIT OR Apache-2.0"
 edition = "2021"
-rust-version = "1.72"  # MSRV
+rust-version = "1.73"  # MSRV
 include = [
   "build.rs",
   "src/**/*",
diff --git a/src/format/diagnostic.rs b/src/format/diagnostic.rs
index 0a2698d..0f254f1 100644
--- a/src/format/diagnostic.rs
+++ b/src/format/diagnostic.rs
@@ -117,6 +117,11 @@ pub enum Applicability {
 #[cfg_attr(feature = "strict_unstable", serde(deny_unknown_fields))]
 #[non_exhaustive]
 pub struct Diagnostic<'a> {
+    /// Can be used to distinguish the different formats.
+    ///
+    /// When parsing, care should be taken to be forwards-compatible with future changes to the format.
+    #[serde(borrow, rename = "$message_type")]
+    pub message_type: Option<CowStr<'a>>,
     /// The error message of this diagnostic.
     #[serde(borrow)]
     pub message: CowStr<'a>,