diff --git a/cliff.toml b/cliff.toml
index 4dba12f..c54ec0b 100644
--- a/cliff.toml
+++ b/cliff.toml
@@ -56,6 +56,7 @@ link_parsers = [
 ]
 
 commit_parsers = [
+  { message = "^api", group = "API change" },
   { message = "^feat", group = "Feature" },
   { message = "^fix", group = "Bugfix" },
   { message = "^tweak", group = "Tweak" },
diff --git a/src/std/core.rs b/src/std/core.rs
index 02206c2..917d4de 100644
--- a/src/std/core.rs
+++ b/src/std/core.rs
@@ -120,7 +120,7 @@ pub trait StdChildWrapper: std::fmt::Debug + Send + Sync {
 	fn start_kill(&mut self) -> Result<()> {
 		#[cfg(unix)]
 		{
-			self.signal(Signal::SIGKILL)
+			self.signal(Signal::SIGKILL as _)
 		}
 
 		#[cfg(not(unix))]
@@ -195,10 +195,10 @@ pub trait StdChildWrapper: std::fmt::Debug + Send + Sync {
 	/// was introduced by command-group to abstract over the signal behaviour between process groups
 	/// and unwrapped processes.
 	#[cfg(unix)]
-	fn signal(&self, sig: Signal) -> Result<()> {
+	fn signal(&self, sig: i32) -> Result<()> {
 		kill(
 			Pid::from_raw(i32::try_from(self.id()).map_err(std::io::Error::other)?),
-			sig,
+			Signal::try_from(sig)?,
 		)
 		.map_err(std::io::Error::from)
 	}
diff --git a/src/std/process_group.rs b/src/std/process_group.rs
index df57b7d..1d0656a 100644
--- a/src/std/process_group.rs
+++ b/src/std/process_group.rs
@@ -45,8 +45,10 @@ impl ProcessGroup {
 	}
 
 	/// Create a process group wrapper attaching the command to an existing process group ID.
-	pub fn attach_to(leader: Pid) -> Self {
-		Self { leader }
+	pub fn attach_to(leader: u32) -> Self {
+		Self {
+			leader: Pid::from_raw(leader as _),
+		}
 	}
 }
 
@@ -71,8 +73,8 @@ impl ProcessGroupChild {
 	/// Get the process group ID of this child process.
 	///
 	/// See: [`man 'setpgid(2)'`](https://www.man7.org/linux/man-pages/man2/setpgid.2.html)
-	pub fn pgid(&self) -> Pid {
-		self.pgid
+	pub fn pgid(&self) -> u32 {
+		self.pgid.as_raw() as _
 	}
 }
 
@@ -215,7 +217,7 @@ impl StdChildWrapper for ProcessGroupChild {
 		}
 	}
 
-	fn signal(&self, sig: Signal) -> Result<()> {
-		self.signal_imp(sig)
+	fn signal(&self, sig: i32) -> Result<()> {
+		self.signal_imp(Signal::try_from(sig)?)
 	}
 }
diff --git a/src/tokio/core.rs b/src/tokio/core.rs
index 17efc98..8ed3311 100644
--- a/src/tokio/core.rs
+++ b/src/tokio/core.rs
@@ -192,11 +192,11 @@ pub trait TokioChildWrapper: std::fmt::Debug + Send + Sync {
 	/// was introduced by command-group to abstract over the signal behaviour between process groups
 	/// and unwrapped processes.
 	#[cfg(unix)]
-	fn signal(&self, sig: Signal) -> Result<()> {
+	fn signal(&self, sig: i32) -> Result<()> {
 		if let Some(id) = self.id() {
 			kill(
 				Pid::from_raw(i32::try_from(id).map_err(std::io::Error::other)?),
-				sig,
+				Signal::try_from(sig)?,
 			)
 			.map_err(std::io::Error::from)
 		} else {
diff --git a/src/tokio/process_group.rs b/src/tokio/process_group.rs
index ac451e2..7a8f93f 100644
--- a/src/tokio/process_group.rs
+++ b/src/tokio/process_group.rs
@@ -78,8 +78,8 @@ impl ProcessGroupChild {
 	/// Get the process group ID of this child process.
 	///
 	/// See: [`man 'setpgid(2)'`](https://www.man7.org/linux/man-pages/man2/setpgid.2.html)
-	pub fn pgid(&self) -> Pid {
-		self.pgid
+	pub fn pgid(&self) -> u32 {
+		self.pgid.as_raw() as _
 	}
 }
 
@@ -242,7 +242,7 @@ impl TokioChildWrapper for ProcessGroupChild {
 		}
 	}
 
-	fn signal(&self, sig: Signal) -> Result<()> {
-		self.signal_imp(sig)
+	fn signal(&self, sig: i32) -> Result<()> {
+		self.signal_imp(Signal::try_from(sig)?)
 	}
 }
diff --git a/tests/std_unix/signals.rs b/tests/std_unix/signals.rs
index ecdda09..71196de 100644
--- a/tests/std_unix/signals.rs
+++ b/tests/std_unix/signals.rs
@@ -7,11 +7,11 @@ fn nowrap() -> Result<()> {
 	})
 	.spawn()?;
 
-	child.signal(Signal::SIGCONT)?;
+	child.signal(Signal::SIGCONT as _)?;
 	sleep(DIE_TIME);
 	assert!(child.try_wait()?.is_none(), "not exited with sigcont");
 
-	child.signal(Signal::SIGTERM)?;
+	child.signal(Signal::SIGTERM as _)?;
 	sleep(DIE_TIME);
 	assert!(child.try_wait()?.is_some(), "exited with sigterm");
 
@@ -26,11 +26,11 @@ fn process_group() -> Result<()> {
 	.wrap(ProcessGroup::leader())
 	.spawn()?;
 
-	child.signal(Signal::SIGCONT)?;
+	child.signal(Signal::SIGCONT as _)?;
 	sleep(DIE_TIME);
 	assert!(child.try_wait()?.is_none(), "not exited with sigcont");
 
-	child.signal(Signal::SIGTERM)?;
+	child.signal(Signal::SIGTERM as _)?;
 	sleep(DIE_TIME);
 	assert!(child.try_wait()?.is_some(), "exited with sigterm");
 
@@ -45,11 +45,11 @@ fn process_session() -> Result<()> {
 	.wrap(ProcessSession)
 	.spawn()?;
 
-	child.signal(Signal::SIGCONT)?;
+	child.signal(Signal::SIGCONT as _)?;
 	sleep(DIE_TIME);
 	assert!(child.try_wait()?.is_none(), "not exited with sigcont");
 
-	child.signal(Signal::SIGTERM)?;
+	child.signal(Signal::SIGTERM as _)?;
 	sleep(DIE_TIME);
 	assert!(child.try_wait()?.is_some(), "exited with sigterm");
 
diff --git a/tests/std_unix/try_wait_twice_after_sigterm.rs b/tests/std_unix/try_wait_twice_after_sigterm.rs
index 3670ec7..00f0a8e 100644
--- a/tests/std_unix/try_wait_twice_after_sigterm.rs
+++ b/tests/std_unix/try_wait_twice_after_sigterm.rs
@@ -8,7 +8,7 @@ fn nowrap() -> Result<()> {
 	.spawn()?;
 	assert!(child.try_wait()?.is_none(), "pre sigterm");
 
-	child.signal(Signal::SIGTERM)?;
+	child.signal(Signal::SIGTERM as _)?;
 	sleep(DIE_TIME);
 	assert!(child.try_wait()?.is_some(), "try_wait() one");
 
@@ -27,7 +27,7 @@ fn process_group() -> Result<()> {
 	.spawn()?;
 	assert!(child.try_wait()?.is_none(), "pre sigterm");
 
-	child.signal(Signal::SIGTERM)?;
+	child.signal(Signal::SIGTERM as _)?;
 	sleep(DIE_TIME);
 	assert!(child.try_wait()?.is_some(), "try_wait() one");
 
@@ -46,7 +46,7 @@ fn process_session() -> Result<()> {
 	.spawn()?;
 	assert!(child.try_wait()?.is_none(), "pre sigterm");
 
-	child.signal(Signal::SIGTERM)?;
+	child.signal(Signal::SIGTERM as _)?;
 	sleep(DIE_TIME);
 	assert!(child.try_wait()?.is_some(), "try_wait() one");
 
diff --git a/tests/std_unix/wait_twice_after_sigterm.rs b/tests/std_unix/wait_twice_after_sigterm.rs
index 03ec783..7cb5165 100644
--- a/tests/std_unix/wait_twice_after_sigterm.rs
+++ b/tests/std_unix/wait_twice_after_sigterm.rs
@@ -8,7 +8,7 @@ fn nowrap() -> Result<()> {
 	.spawn()?;
 	assert!(child.try_wait()?.is_none(), "pre sigterm");
 
-	child.signal(Signal::SIGTERM)?;
+	child.signal(Signal::SIGTERM as _)?;
 
 	let status = (child.wait())?;
 	assert_eq!(status.signal(), Some(Signal::SIGTERM as i32), "wait() one");
@@ -28,7 +28,7 @@ fn process_group() -> Result<()> {
 	.spawn()?;
 	assert!(child.try_wait()?.is_none(), "pre sigterm");
 
-	child.signal(Signal::SIGTERM)?;
+	child.signal(Signal::SIGTERM as _)?;
 
 	let status = (child.wait())?;
 	assert_eq!(status.signal(), Some(Signal::SIGTERM as i32), "wait() one");
@@ -48,7 +48,7 @@ fn process_session() -> Result<()> {
 	.spawn()?;
 	assert!(child.try_wait()?.is_none(), "pre sigterm");
 
-	child.signal(Signal::SIGTERM)?;
+	child.signal(Signal::SIGTERM as _)?;
 
 	let status = (child.wait())?;
 	assert_eq!(status.signal(), Some(Signal::SIGTERM as i32), "wait() one");
diff --git a/tests/tokio_unix/signals.rs b/tests/tokio_unix/signals.rs
index a5a49ba..4de5e71 100644
--- a/tests/tokio_unix/signals.rs
+++ b/tests/tokio_unix/signals.rs
@@ -7,11 +7,11 @@ async fn nowrap() -> Result<()> {
 	})
 	.spawn()?;
 
-	child.signal(Signal::SIGCONT)?;
+	child.signal(Signal::SIGCONT as _)?;
 	sleep(DIE_TIME).await;
 	assert!(child.try_wait()?.is_none(), "not exited with sigcont");
 
-	child.signal(Signal::SIGTERM)?;
+	child.signal(Signal::SIGTERM as _)?;
 	sleep(DIE_TIME).await;
 	assert!(child.try_wait()?.is_some(), "exited with sigterm");
 
@@ -26,11 +26,11 @@ async fn process_group() -> Result<()> {
 	.wrap(ProcessGroup::leader())
 	.spawn()?;
 
-	child.signal(Signal::SIGCONT)?;
+	child.signal(Signal::SIGCONT as _)?;
 	sleep(DIE_TIME).await;
 	assert!(child.try_wait()?.is_none(), "not exited with sigcont");
 
-	child.signal(Signal::SIGTERM)?;
+	child.signal(Signal::SIGTERM as _)?;
 	sleep(DIE_TIME).await;
 	assert!(child.try_wait()?.is_some(), "exited with sigterm");
 
@@ -45,11 +45,11 @@ async fn process_session() -> Result<()> {
 	.wrap(ProcessSession)
 	.spawn()?;
 
-	child.signal(Signal::SIGCONT)?;
+	child.signal(Signal::SIGCONT as _)?;
 	sleep(DIE_TIME).await;
 	assert!(child.try_wait()?.is_none(), "not exited with sigcont");
 
-	child.signal(Signal::SIGTERM)?;
+	child.signal(Signal::SIGTERM as _)?;
 	sleep(DIE_TIME).await;
 	assert!(child.try_wait()?.is_some(), "exited with sigterm");
 
diff --git a/tests/tokio_unix/try_wait_twice_after_sigterm.rs b/tests/tokio_unix/try_wait_twice_after_sigterm.rs
index 789de5a..39a0415 100644
--- a/tests/tokio_unix/try_wait_twice_after_sigterm.rs
+++ b/tests/tokio_unix/try_wait_twice_after_sigterm.rs
@@ -8,7 +8,7 @@ async fn nowrap() -> Result<()> {
 	.spawn()?;
 	assert!(child.try_wait()?.is_none(), "pre sigterm");
 
-	child.signal(Signal::SIGTERM)?;
+	child.signal(Signal::SIGTERM as _)?;
 	sleep(DIE_TIME).await;
 	assert!(child.try_wait()?.is_some(), "try_wait() one");
 
@@ -27,7 +27,7 @@ async fn process_group() -> Result<()> {
 	.spawn()?;
 	assert!(child.try_wait()?.is_none(), "pre sigterm");
 
-	child.signal(Signal::SIGTERM)?;
+	child.signal(Signal::SIGTERM as _)?;
 	sleep(DIE_TIME).await;
 	assert!(child.try_wait()?.is_some(), "try_wait() one");
 
@@ -46,7 +46,7 @@ async fn process_session() -> Result<()> {
 	.spawn()?;
 	assert!(child.try_wait()?.is_none(), "pre sigterm");
 
-	child.signal(Signal::SIGTERM)?;
+	child.signal(Signal::SIGTERM as _)?;
 	sleep(DIE_TIME).await;
 	assert!(child.try_wait()?.is_some(), "try_wait() one");
 
diff --git a/tests/tokio_unix/wait_twice_after_sigterm.rs b/tests/tokio_unix/wait_twice_after_sigterm.rs
index 7949fb4..2b2e7d7 100644
--- a/tests/tokio_unix/wait_twice_after_sigterm.rs
+++ b/tests/tokio_unix/wait_twice_after_sigterm.rs
@@ -8,7 +8,7 @@ async fn nowrap() -> Result<()> {
 	.spawn()?;
 	assert!(child.try_wait()?.is_none(), "pre sigterm");
 
-	child.signal(Signal::SIGTERM)?;
+	child.signal(Signal::SIGTERM as _)?;
 
 	let status = Box::into_pin(child.wait()).await?;
 	assert_eq!(status.signal(), Some(Signal::SIGTERM as i32), "wait() one");
@@ -28,7 +28,7 @@ async fn process_group() -> Result<()> {
 	.spawn()?;
 	assert!(child.try_wait()?.is_none(), "pre sigterm");
 
-	child.signal(Signal::SIGTERM)?;
+	child.signal(Signal::SIGTERM as _)?;
 
 	let status = Box::into_pin(child.wait()).await?;
 	assert_eq!(status.signal(), Some(Signal::SIGTERM as i32), "wait() one");
@@ -48,7 +48,7 @@ async fn process_session() -> Result<()> {
 	.spawn()?;
 	assert!(child.try_wait()?.is_none(), "pre sigterm");
 
-	child.signal(Signal::SIGTERM)?;
+	child.signal(Signal::SIGTERM as _)?;
 
 	let status = Box::into_pin(child.wait()).await?;
 	assert_eq!(status.signal(), Some(Signal::SIGTERM as i32), "wait() one");