diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 472366db..008c2b52 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -27,7 +27,7 @@ jobs:
         rust: [nightly, beta, stable, 1.52.0, 1.46.0, 1.40.0, 1.39.0, 1.36.0, 1.33.0, 1.32.0, 1.31.0]
     timeout-minutes: 45
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: dtolnay/rust-toolchain@master
         with:
           toolchain: ${{matrix.rust}}
@@ -46,7 +46,7 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 45
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: dtolnay/rust-toolchain@stable
       - run: npm install semver
       - run: cargo test
@@ -60,7 +60,7 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 45
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: dtolnay/rust-toolchain@nightly
       - run: cargo generate-lockfile -Z minimal-versions
       - run: cargo check --locked --features serde
@@ -71,7 +71,7 @@ jobs:
     if: github.event_name != 'pull_request'
     timeout-minutes: 45
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: dtolnay/rust-toolchain@clippy
       - run: cargo clippy --tests --benches -- -Dclippy::all -Dclippy::pedantic
 
@@ -84,7 +84,7 @@ jobs:
       MIRIFLAGS: -Zmiri-strict-provenance
     timeout-minutes: 45
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: dtolnay/rust-toolchain@miri
       - name: Run cargo miri test (64-bit little endian)
         run: cargo miri test --target x86_64-unknown-linux-gnu
@@ -102,7 +102,7 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 45
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: dtolnay/rust-toolchain@nightly
       - uses: dtolnay/install@cargo-fuzz
       - run: cargo fuzz check
@@ -113,7 +113,7 @@ jobs:
     if: github.event_name != 'pull_request'
     timeout-minutes: 45
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: dtolnay/install@cargo-outdated
       - run: cargo outdated --workspace --exit-code 1
       - run: cargo outdated --manifest-path fuzz/Cargo.toml --exit-code 1
diff --git a/Cargo.toml b/Cargo.toml
index 863f7386..f40e9521 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "semver"
-version = "1.0.18"
+version = "1.0.19"
 authors = ["David Tolnay <dtolnay@gmail.com>"]
 categories = ["data-structures", "no-std"]
 description = "Parser and evaluator for Cargo's flavor of Semantic Versioning"
diff --git a/src/impls.rs b/src/impls.rs
index c3b6c601..cc4fd415 100644
--- a/src/impls.rs
+++ b/src/impls.rs
@@ -38,13 +38,13 @@ impl Deref for BuildMetadata {
 
 impl PartialOrd for Prerelease {
     fn partial_cmp(&self, rhs: &Self) -> Option<Ordering> {
-        Some(Ord::cmp(self, rhs))
+        Some(self.cmp(rhs))
     }
 }
 
 impl PartialOrd for BuildMetadata {
     fn partial_cmp(&self, rhs: &Self) -> Option<Ordering> {
-        Some(Ord::cmp(self, rhs))
+        Some(self.cmp(rhs))
     }
 }
 
diff --git a/src/lib.rs b/src/lib.rs
index d2c4eb37..88f24383 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -60,7 +60,7 @@
 //!
 //! [Specifying Dependencies]: https://doc.rust-lang.org/cargo/reference/specifying-dependencies.html
 
-#![doc(html_root_url = "https://docs.rs/semver/1.0.18")]
+#![doc(html_root_url = "https://docs.rs/semver/1.0.19")]
 #![cfg_attr(doc_cfg, feature(doc_cfg))]
 #![cfg_attr(all(not(feature = "std"), not(no_alloc_crate)), no_std)]
 #![cfg_attr(not(no_unsafe_op_in_unsafe_fn_lint), deny(unsafe_op_in_unsafe_fn))]
diff --git a/tests/test_identifier.rs b/tests/test_identifier.rs
index dc888c9c..40d85965 100644
--- a/tests/test_identifier.rs
+++ b/tests/test_identifier.rs
@@ -43,3 +43,9 @@ fn test_eq() {
     assert_ne!(prerelease("aaaaaaaaa"), prerelease("bbbbbbbbb"));
     assert_ne!(build_metadata("1"), build_metadata("001"));
 }
+
+#[test]
+fn test_prerelease() {
+    let err = prerelease_err("1.b\0");
+    assert_to_string(err, "unexpected character in pre-release identifier");
+}
diff --git a/tests/test_version.rs b/tests/test_version.rs
index de3628fa..991087f7 100644
--- a/tests/test_version.rs
+++ b/tests/test_version.rs
@@ -47,6 +47,18 @@ fn test_parse() {
     let err = version_err("1.2.3-01");
     assert_to_string(err, "invalid leading zero in pre-release identifier");
 
+    let err = version_err("1.2.3++");
+    assert_to_string(err, "empty identifier segment in build metadata");
+
+    let err = version_err("07");
+    assert_to_string(err, "invalid leading zero in major version number");
+
+    let err = version_err("111111111111111111111.0.0");
+    assert_to_string(err, "value of major version number exceeds u64::MAX");
+
+    let err = version_err("8\0");
+    assert_to_string(err, "unexpected character '\\0' after major version number");
+
     let parsed = version("1.2.3");
     let expected = Version::new(1, 2, 3);
     assert_eq!(parsed, expected);
diff --git a/tests/test_version_req.rs b/tests/test_version_req.rs
index 98a03ac8..1ed2358a 100644
--- a/tests/test_version_req.rs
+++ b/tests/test_version_req.rs
@@ -168,6 +168,9 @@ pub fn test_multiple() {
     // https://github.com/steveklabnik/semver/issues/56
     let err = req_err("1.2.3 - 2.3.4");
     assert_to_string(err, "expected comma after patch version number, found '-'");
+
+    let err = req_err(">1, >2, >3, >4, >5, >6, >7, >8, >9, >10, >11, >12, >13, >14, >15, >16, >17, >18, >19, >20, >21, >22, >23, >24, >25, >26, >27, >28, >29, >30, >31, >32, >33");
+    assert_to_string(err, "excessive number of version comparators");
 }
 
 #[test]
@@ -332,7 +335,7 @@ pub fn test_pre() {
 }
 
 #[test]
-pub fn test_parse_errors() {
+pub fn test_parse() {
     let err = req_err("\0");
     assert_to_string(
         err,
@@ -367,6 +370,45 @@ pub fn test_parse_errors() {
     );
 }
 
+#[test]
+fn test_comparator_parse() {
+    let parsed = comparator("1.2.3-alpha");
+    assert_to_string(parsed, "^1.2.3-alpha");
+
+    let parsed = comparator("2.X");
+    assert_to_string(parsed, "2.*");
+
+    let parsed = comparator("2");
+    assert_to_string(parsed, "^2");
+
+    let parsed = comparator("2.x.x");
+    assert_to_string(parsed, "2.*");
+
+    let err = comparator_err("1.2.3-01");
+    assert_to_string(err, "invalid leading zero in pre-release identifier");
+
+    let err = comparator_err("1.2.3+4.");
+    assert_to_string(err, "empty identifier segment in build metadata");
+
+    let err = comparator_err(">");
+    assert_to_string(
+        err,
+        "unexpected end of input while parsing major version number",
+    );
+
+    let err = comparator_err("1.");
+    assert_to_string(
+        err,
+        "unexpected end of input while parsing minor version number",
+    );
+
+    let err = comparator_err("1.*.");
+    assert_to_string(err, "unexpected character after wildcard in version req");
+
+    let err = comparator_err("1.2.3+4ÿ");
+    assert_to_string(err, "unexpected character 'ÿ' after build metadata");
+}
+
 #[test]
 fn test_cargo3202() {
     let ref r = req("0.*.*");
diff --git a/tests/util/mod.rs b/tests/util/mod.rs
index 5cc142c4..07d691fa 100644
--- a/tests/util/mod.rs
+++ b/tests/util/mod.rs
@@ -1,6 +1,6 @@
 #![allow(dead_code)]
 
-use semver::{BuildMetadata, Error, Prerelease, Version, VersionReq};
+use semver::{BuildMetadata, Comparator, Error, Prerelease, Version, VersionReq};
 use std::fmt::Display;
 
 #[cfg_attr(not(no_track_caller), track_caller)]
@@ -23,11 +23,26 @@ pub(super) fn req_err(text: &str) -> Error {
     VersionReq::parse(text).unwrap_err()
 }
 
+#[cfg_attr(not(no_track_caller), track_caller)]
+pub(super) fn comparator(text: &str) -> Comparator {
+    Comparator::parse(text).unwrap()
+}
+
+#[cfg_attr(not(no_track_caller), track_caller)]
+pub(super) fn comparator_err(text: &str) -> Error {
+    Comparator::parse(text).unwrap_err()
+}
+
 #[cfg_attr(not(no_track_caller), track_caller)]
 pub(super) fn prerelease(text: &str) -> Prerelease {
     Prerelease::new(text).unwrap()
 }
 
+#[cfg_attr(not(no_track_caller), track_caller)]
+pub(super) fn prerelease_err(text: &str) -> Error {
+    Prerelease::new(text).unwrap_err()
+}
+
 #[cfg_attr(not(no_track_caller), track_caller)]
 pub(super) fn build_metadata(text: &str) -> BuildMetadata {
     BuildMetadata::new(text).unwrap()