diff --git a/Sources/SSDPClient/SSDPService.swift b/Sources/SSDPClient/SSDPService.swift
index c8d5003..49a3190 100644
--- a/Sources/SSDPClient/SSDPService.swift
+++ b/Sources/SSDPClient/SSDPService.swift
@@ -48,7 +48,7 @@ public class SSDPService {
     private func parse(_ response: String) -> [String: String] {
         var result = [String: String]()
         
-        let matches = HeaderRegex.matches(in: response, range: NSRange(location: 0, length: response.count))
+        let matches = HeaderRegex.matches(in: response, range: NSRange(location: 0, length: response.utf16.count))
         for match in matches {
             let keyCaptureGroupIndex = match.range(at: 1)
             let key = (response as NSString).substring(with: keyCaptureGroupIndex)
diff --git a/Tests/SSDPClientTests/SSDPServiceTests.swift b/Tests/SSDPClientTests/SSDPServiceTests.swift
index beedccd..cace27d 100644
--- a/Tests/SSDPClientTests/SSDPServiceTests.swift
+++ b/Tests/SSDPClientTests/SSDPServiceTests.swift
@@ -39,7 +39,7 @@ class SSDPServiceTests: XCTestCase {
         XCTAssertNotNil(service.location)
         XCTAssertEqual("http://192.168.1.1:10000/root.xml", service.location)
         XCTAssertEqual("max-age=120", service.responseHeaders?["CACHE-CONTROL"])
-        XCTAssertEqual("\"http://schemas.upnp.org/upnp/1/0/\"; ", service.responseHeaders?["OPT"])
+        XCTAssertEqual("\"http://schemas.upnp.org/upnp/1/0/\"; ns=01", service.responseHeaders?["OPT"])
     }
     
     func testParseCaseInsensitive() {
@@ -55,6 +55,6 @@ class SSDPServiceTests: XCTestCase {
         XCTAssertNotNil(service.location)
         XCTAssertEqual("http://192.168.1.1:10000/root.xml", service.location)
         XCTAssertEqual("max-age=120", service.responseHeaders?["CACHE-CONTROL"])
-        XCTAssertEqual("\"http://schemas.upnp.org/upnp/1/0/\"; ", service.responseHeaders?["OPT"])
+        XCTAssertEqual("\"http://schemas.upnp.org/upnp/1/0/\"; ns=01", service.responseHeaders?["OPT"])
     }
 }