diff --git a/CHANGELOG.md b/CHANGELOG.md
index f04d1bcd..280becaf 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -14,6 +14,7 @@ All notable changes to this project will be documented in this file.
 
 ### Fixes
 
+- Fixed signature verification if a signed header contains a non ASCII character.
 - Fixed support for Thunderbird Conversations add-on in Thunderbird 115 and later (#395).
 
 ### Other
diff --git a/modules/dkim/crypto.mjs.js b/modules/dkim/crypto.mjs.js
index bb12babd..f9673dfb 100644
--- a/modules/dkim/crypto.mjs.js
+++ b/modules/dkim/crypto.mjs.js
@@ -229,7 +229,7 @@ class DkimCryptoWeb extends DkimCryptoBase {
 			"RSASSA-PKCS1-v1_5",
 			cryptoKey,
 			this._decodeBase64(signature),
-			new TextEncoder().encode(data)
+			strToArrayBuffer(data)
 		);
 		return [valid, rsaKeyParams.modulusLength];
 	}
diff --git a/test/data/dkim/header_with_non_ascii_char.eml b/test/data/dkim/header_with_non_ascii_char.eml
new file mode 100644
index 00000000..5e74775f
--- /dev/null
+++ b/test/data/dkim/header_with_non_ascii_char.eml
@@ -0,0 +1,18 @@
+DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=example.com; i=@example.com; 
+ q=dns/txt; s=brisbane; t=1698597711; h=from : to : subject : date : 
+ message-id : from : subject : date; 
+ bh=2jUSOH9NhtVGCQWNr9BrIAPreKQjO6Sn7XIkfJVOzv8=; 
+ b=CE3Oslfk2qB38RAmRCRhIIbMvP5u/kuP1KEswe4Gx2qSScrl/cZm2WCstkEbcapJxH6qu0
+ Xw/AE7TWypWitV46qscm2GrDVselmWoSmxFl9Sji1p/5ouWc2UQJGNSDUYCpMJN0T3UMVHYv
+ +Bx0myqvZbYbKXp6jZsPami5g1Xcg=
+From: Joe SixPack <joe@example.com>
+To: Suzie ß <suzie@shopping.example.net>
+Subject: DKIM test - To header with non ASCII char
+Date: Fri, 11 Jul 2003 21:00:37 -0700 (PDT)
+Message-ID: <20030712040037.46341.5F8J+test_0001@example.com>
+
+Hi.
+
+We lost the game. Are you hungry yet?
+
+Joe.
diff --git a/test/unittest/verifierSpec.mjs.js b/test/unittest/verifierSpec.mjs.js
index 93ebfd56..d95a9720 100644
--- a/test/unittest/verifierSpec.mjs.js
+++ b/test/unittest/verifierSpec.mjs.js
@@ -75,6 +75,12 @@ describe("DKIM Verifier [unittest]", function () {
 			expect(res.signatures[1]?.auid).to.be.equal("@football.example.com");
 			expect(res.signatures[1]?.selector).to.be.equal("brisbane");
 		});
+		it("Signed header with non ASCII char", async function () {
+			const res = await verifyEmlFile("dkim/header_with_non_ascii_char.eml");
+			expect(res.signatures.length).to.be.equal(1);
+			expect(res.signatures[0]?.result).to.be.equal("SUCCESS");
+			expect(res.signatures[0]?.warnings).to.be.empty;
+		});
 		it("DKIM key with empty notes tag", async function () {
 			const res = await verifyEmlFile("rfc6376-A.2.eml", new Map([
 				["brisbane._domainkey.example.com",