diff --git a/src/algorithm.rs b/src/algorithm.rs
index 6bd8873..0fd63ab 100644
--- a/src/algorithm.rs
+++ b/src/algorithm.rs
@@ -28,6 +28,13 @@ impl Algorithm {
 		}
 	}
 
+	pub fn key_type(&self) -> String {
+		match self {
+			Self::Ed25519Sha256 => String::from("ed25519"),
+			Self::Rsa2048Sha256 | Self::Rsa3072Sha256 | Self::Rsa4096Sha256 => String::from("rsa"),
+		}
+	}
+
 	pub fn gen_keys(&self) -> (String, String) {
 		match self {
 			Self::Ed25519Sha256 => gen_ed25519_kp(),
diff --git a/src/signature.rs b/src/signature.rs
index 13fc5d6..ea96ebc 100644
--- a/src/signature.rs
+++ b/src/signature.rs
@@ -43,8 +43,9 @@ impl Signature {
 
 	pub fn get_header(&self) -> String {
 		format!(
-			"DKIM-Signature: v=1; a={algorithm}; c={canonicalization}; d={sdid};\r\n\tt={timestamp}; s={selector};\r\n\th={headers};\r\n\tbh={body_hash};\r\n\tb={signature}",
+			"DKIM-Signature: v=1; a={algorithm}; c={canonicalization}; k={key_type};\r\n\tt={timestamp}; d={sdid};\r\n\ts={selector};\r\n\th={headers};\r\n\tbh={body_hash};\r\n\tb={signature}",
 			algorithm=self.algorithm.display(),
+			key_type=self.algorithm.key_type(),
 			canonicalization=self.canonicalization.to_string(),
 			selector=self.selector,
 			sdid=self.sdid,