diff --git a/src/hash.rs b/src/hash.rs
index cadb40e0..85d0703c 100644
--- a/src/hash.rs
+++ b/src/hash.rs
@@ -6,6 +6,7 @@ use crate::canonicalization::{
     self, canonicalize_body_relaxed, canonicalize_body_simple, canonicalize_header_relaxed,
     canonicalize_header_simple,
 };
+use crate::header::HEADER;
 use crate::{bytes, DKIMError, DKIMHeader};
 
 #[derive(Debug, Clone)]
@@ -111,12 +112,16 @@ pub(crate) fn compute_headers_hash<'a, 'b>(
     {
         let sign = dkim_header.get_raw_tag("b").unwrap();
         let value = dkim_header.raw_bytes.replace(&sign, "");
-        if canonicalization_type == canonicalization::Type::Simple {
-            input.extend_from_slice(&"DKIM-Signature: ".as_bytes());
+        let mut canonicalized_value = if canonicalization_type == canonicalization::Type::Simple {
+            canonicalize_header_simple(HEADER, &value.as_bytes())
         } else {
-            input.extend_from_slice(&"dkim-signature:".as_bytes());
-        }
-        input.extend_from_slice(&value.as_bytes());
+            canonicalize_header_relaxed(HEADER, &value.as_bytes())
+        };
+
+        // remove trailing "\r\n"
+        canonicalized_value.truncate(canonicalized_value.len() - 2);
+
+        input.extend_from_slice(&canonicalized_value);
     }
     debug!(logger, "headers to hash: {:?}", input);
 
diff --git a/src/lib.rs b/src/lib.rs
index b2c9ff2e..c7b201f6 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -414,7 +414,15 @@ We lost the game.  Are you hungry yet?
 
 Joe."#
             .replace("\n", "\r\n");
-        let raw_header_dkim = r#"v=1; a=ed25519-sha256; c=relaxed/relaxed; d=football.example.com; i=@football.example.com; q=dns/txt; s=brisbane; t=1528637909; h=from : to : subject : date : message-id : from : subject : date; bh=2jUSOH9NhtVGCQWNr9BrIAPreKQjO6Sn7XIkfJVOzv8=; b=/gCrinpcQOoIfuHNQIbq4pgh9kyIK3AQUdt9OdqQehSwhEIug4D11BusFa3bT3FY5OsU7ZbnKELq+eXdp1Q1Dw=="#;
+
+        let email = mailparse::parse_mail(raw_email.as_bytes()).unwrap();
+        let h = email
+            .headers
+            .get_all_headers(HEADER)
+            .first()
+            .unwrap()
+            .get_value_raw();
+        let raw_header_dkim = String::from_utf8_lossy(h);
 
         let resolver: Arc<dyn Lookup> = Arc::new(MockResolver::new());
 
@@ -422,7 +430,7 @@ Joe."#
             &slog::Logger::root(slog::Discard, slog::o!()),
             Arc::clone(&resolver),
             &validate_header(&raw_header_dkim).unwrap(),
-            &mailparse::parse_mail(raw_email.as_bytes()).unwrap(),
+            &email,
         )
         .await;