diff --git a/src/canonicalization.rs b/src/canonicalization.rs
index fa3950d..b90460e 100644
--- a/src/canonicalization.rs
+++ b/src/canonicalization.rs
@@ -1,3 +1,6 @@
+use std::str::FromStr;
+
+#[derive(Clone, Copy, Debug)]
 pub enum CanonicalizationType {
 	Relaxed,
 	Simple,
@@ -9,7 +12,28 @@ impl Default for CanonicalizationType {
 	}
 }
 
-#[derive(Default)]
+impl ToString for CanonicalizationType {
+	fn to_string(&self) -> String {
+		match self {
+			CanonicalizationType::Relaxed => String::from("relaxed"),
+			CanonicalizationType::Simple => String::from("simple"),
+		}
+	}
+}
+
+impl FromStr for CanonicalizationType {
+	type Err = String;
+
+	fn from_str(s: &str) -> Result<Self, Self::Err> {
+		match s.to_lowercase().as_str() {
+			"relaxed" => Ok(CanonicalizationType::Relaxed),
+			"simple" => Ok(CanonicalizationType::Simple),
+			_ => Err(format!("{s}: invalid canonicalization type")),
+		}
+	}
+}
+
+#[derive(Clone, Copy, Debug, Default)]
 pub struct Canonicalization {
 	header_alg: CanonicalizationType,
 	body_alg: CanonicalizationType,
@@ -41,6 +65,31 @@ impl Canonicalization {
 	}
 }
 
+impl ToString for Canonicalization {
+	fn to_string(&self) -> String {
+		format!(
+			"{}/{}",
+			self.header_alg.to_string(),
+			self.body_alg.to_string()
+		)
+	}
+}
+
+impl FromStr for Canonicalization {
+	type Err = String;
+
+	fn from_str(s: &str) -> Result<Self, Self::Err> {
+		let elems: Vec<&str> = s.split('/').collect();
+		if elems.len() != 2 {
+			return Err(format!("{s}: invalid canonicalization"));
+		}
+		Ok(Self {
+			header_alg: elems[0].parse()?,
+			body_alg: elems[1].parse()?,
+		})
+	}
+}
+
 fn to_lowercase(c: &mut u8) {
 	if *c >= b'A' && *c <= b'Z' {
 		*c += 32
diff --git a/src/config.rs b/src/config.rs
index 76beea1..7098bbf 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -1,3 +1,4 @@
+use crate::canonicalization::Canonicalization;
 use clap::Parser;
 use std::collections::HashSet;
 use std::fs::File;
@@ -8,6 +9,8 @@ use std::path::PathBuf;
 #[derive(Parser, Debug)]
 #[command(author, version, about, long_about = None)]
 pub struct Config {
+	#[arg(short, long, default_value_t = Canonicalization::default())]
+	canonicalization: Canonicalization,
 	#[arg(short, long)]
 	domain: Vec<String>,
 	#[arg(short = 'D', long, value_name = "FILE")]
@@ -34,6 +37,10 @@ impl Config {
 		Ok(cnf)
 	}
 
+	pub fn canonicalization(&self) -> Canonicalization {
+		self.canonicalization
+	}
+
 	pub fn domains(&self) -> &[String] {
 		&self.domain
 	}