diff --git a/scanner/Sources/WifiScanner.swift b/scanner/Sources/WifiScanner.swift
index f58d911..5322709 100644
--- a/scanner/Sources/WifiScanner.swift
+++ b/scanner/Sources/WifiScanner.swift
@@ -138,7 +138,14 @@ func mapBand(_ b: CWChannelBand) -> UInt8 {
     switch b.rawValue { case 1: return 1; case 2: return 2; case 3: return 3; default: return 0 }
 }
 func mapWidth(_ w: CWChannelWidth) -> UInt16 {
-    switch w.rawValue { case 0: return 20; case 1: return 40; case 2: return 80; case 3: return 160; default: return 0 }
+    switch w {
+    case .widthUnknown: return 0
+    case .width20MHz: return 20
+    case .width40MHz: return 40
+    case .width80MHz: return 80
+    case .width160MHz: return 160
+    @unknown default: return 0
+    }
 }
 func detectSecurity(_ n: CWNetwork) -> UInt8 {
     let probes: [(CWSecurity, UInt8)] = [
diff --git a/scanner/Tests/WifiScannerTests.swift b/scanner/Tests/WifiScannerTests.swift
index b3ea3ff..2169f5e 100644
--- a/scanner/Tests/WifiScannerTests.swift
+++ b/scanner/Tests/WifiScannerTests.swift
@@ -1,5 +1,6 @@
 import Darwin
 import Foundation
+import CoreWLAN
 
 struct TestFailure: Error, CustomStringConvertible {
     let message: String
@@ -107,6 +108,24 @@ func testParseBSSIDRejectsMissingInvalidOrShortValues() throws {
     try expectEqual(parseBSSID("01:23:45:67:89:xx"), Data(), "invalid BSSID should parse as empty data")
 }
 
+func testMapWidthUsesCoreWLANChannelWidthConstants() throws {
+    let cases: [(CWChannelWidth, UInt16, String)] = [
+        (.widthUnknown, 0, "unknown"),
+        (.width20MHz, 20, "20 MHz"),
+        (.width40MHz, 40, "40 MHz"),
+        (.width80MHz, 80, "80 MHz"),
+        (.width160MHz, 160, "160 MHz"),
+    ]
+
+    for (width, expectedWidth, name) in cases {
+        try expectEqual(
+            mapWidth(width),
+            expectedWidth,
+            "mapWidth should convert CoreWLAN \(name) channel width"
+        )
+    }
+}
+
 func testEncodePasswordResponseMatchesWireFormat() throws {
     let response = encodePasswordResponse(password: "secret", error: "denied")
 
@@ -180,6 +199,7 @@ struct WifiScannerTestRunner {
             ("writeAll writes full payloads", testWriteAllWritesFullPayload),
             ("parseBSSID accepts valid hex octets", testParseBSSIDAcceptsHexOctets),
             ("parseBSSID rejects invalid values", testParseBSSIDRejectsMissingInvalidOrShortValues),
+            ("mapWidth uses CoreWLAN channel width constants", testMapWidthUsesCoreWLANChannelWidthConstants),
             ("encodePasswordResponse matches wire format", testEncodePasswordResponseMatchesWireFormat),
             ("encodeScanResponse matches wire format", testEncodeScanResponseMatchesWireFormat),
         ]