diff --git a/passKit/Parser/Constants.swift b/passKit/Parser/Constants.swift
index c5835f2..c10f4f6 100644
--- a/passKit/Parser/Constants.swift
+++ b/passKit/Parser/Constants.swift
@@ -58,7 +58,8 @@ public struct Constants {
     }
 
     static func isUnknown(_ string: String) -> Bool {
-        return string.starts(with: UNKNOWN)
+        let components = string.components(separatedBy: " ")
+        return components.count == 2 && components[0] == UNKNOWN && UInt(components[1]) != nil
     }
 
     static func unknown(_ number: UInt) -> String {
diff --git a/passKitTests/Parser/ConstantsTest.swift b/passKitTests/Parser/ConstantsTest.swift
index 711ee80..1ff1771 100644
--- a/passKitTests/Parser/ConstantsTest.swift
+++ b/passKitTests/Parser/ConstantsTest.swift
@@ -27,10 +27,13 @@ class ConstantsTest: XCTestCase {
     }
 
     func testIsUnknown() {
-        XCTAssert(Constants.isUnknown("unknown"))
-        XCTAssert(Constants.isUnknown("unknown string"))
+        XCTAssert(Constants.isUnknown("unknown 1"))
+        XCTAssert(Constants.isUnknown("unknown 435"))
         XCTAssertFalse(Constants.isUnknown("otp"))
-        XCTAssertFalse(Constants.isUnknown("Unknown"))
+        XCTAssertFalse(Constants.isUnknown("unknown "))
+        XCTAssertFalse(Constants.isUnknown("unknown something"))
+        XCTAssertFalse(Constants.isUnknown("unknown 123 something"))
+        XCTAssertFalse(Constants.isUnknown("Unknown 1"))
     }
 
     func testUnknown() {