diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 11c836b..f6d600b 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -125,3 +125,20 @@ jobs:
         run: swift build --build-tests
       - name: Test
         run: swift test --skip-build
+
+  windows_swift_6_1:
+    runs-on: windows-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      - name: Install Swift
+        uses: SwiftyLab/setup-swift@latest
+        with:
+          swift-version: "6.1.2"
+          visual-studio-components: Microsoft.VisualStudio.Component.Windows11SDK.22621
+      - name: Version
+        run: swift --version
+      - name: Build
+        run: swift build --build-tests
+      - name: Test
+        run: swift test --skip-build
diff --git a/Sources/KeyValueDecoder.swift b/Sources/KeyValueDecoder.swift
index 5d0794d..6cef1a4 100644
--- a/Sources/KeyValueDecoder.swift
+++ b/Sources/KeyValueDecoder.swift
@@ -29,7 +29,6 @@
 //  SOFTWARE.
 //
 
-import CoreFoundation
 import Foundation
 
 /// Top level encoder that converts `[String: Any]`, `[Any]` or `Any` into `Codable` types.
@@ -779,22 +778,44 @@ extension NSNumber {
         }
     }
 
-    func getNumberTypeID() -> CFNumberType? {
-        guard CFGetTypeID(self as CFTypeRef) == CFNumberGetTypeID() else { return nil }
-#if canImport(Darwin)
-        return CFNumberGetType(self as CFNumber)
-#else
-        guard type(of: self) != type(of: NSNumber(true)) else { return nil }
+    enum NumberTypeID: Int, Sendable {
+        case sInt8Type       = 1
+        case sInt16Type      = 2
+        case sInt32Type      = 3
+        case sInt64Type      = 4
+        case float32Type     = 5
+        case float64Type     = 6
+        case charType        = 7
+        case shortType       = 8
+        case intType         = 9
+        case longType        = 10
+        case longLongType    = 11
+        case floatType       = 12
+        case doubleType      = 13
+        case cfIndexType     = 14
+        case nsIntegerType   = 15
+        case cgFloatType     = 16
+    }
+
+    func getNumberTypeID() -> NumberTypeID? {
+        // Prevent misclassifying Bool as charType
+        if type(of: self) == type(of: NSNumber(value: true)) { return nil }
+
         switch String(cString: objCType) {
-        case "c": return CFNumberType.charType
-        case "s": return CFNumberType.shortType
-        case "i": return CFNumberType.intType
-        case "q": return CFNumberType.longLongType
-        case "d": return CFNumberType.doubleType
-        case "f": return CFNumberType.floatType
-        case "Q": return CFNumberType.longLongType
-        default: return nil
+        case "c": return .charType
+        case "C": return .sInt8Type
+        case "s": return .shortType
+        case "S": return .sInt16Type
+        case "i": return .intType
+        case "I": return .sInt32Type
+        case "l": return .longType
+        case "L": return .sInt32Type
+        case "q": return .longLongType
+        case "Q": return .sInt64Type
+        case "f": return .floatType
+        case "d": return .doubleType
+        case "B": return nil
+        default:  return nil
         }
-#endif
     }
 }
diff --git a/Tests/KeyValueDecoderTests.swift b/Tests/KeyValueDecoderTests.swift
index 09e94a7..a0d58cf 100644
--- a/Tests/KeyValueDecoderTests.swift
+++ b/Tests/KeyValueDecoderTests.swift
@@ -892,7 +892,47 @@ struct KeyValueDecoderTests {
         #expect((true as NSNumber).getDoubleValue() == nil)
     }
 
-    @Test
+#if compiler(>=6.1)
+    @Test()
+    func decodingErrors() throws {
+
+        var error = #expect(throws: DecodingError.self) {
+            try KeyValueDecoder.decode(Seafood.self, from: 10)
+        }
+        #expect(error?.debugDescription == "Expected String at SELF, found Int")
+
+        error = #expect(throws: DecodingError.self) {
+            try KeyValueDecoder.decode(Seafood.self, from: 10)
+        }
+        #expect(error?.debugDescription == "Expected String at SELF, found Int")
+
+        error = #expect(throws: DecodingError.self) {
+            try KeyValueDecoder.decode(Int.self, from: NSNull())
+        }
+        #expect(error?.debugDescription == "Expected BinaryInteger at SELF, found NSNull")
+
+        error = #expect(throws: DecodingError.self) {
+            try KeyValueDecoder.decode(Int.self, from: Optional<Int>.none)
+        }
+        #expect(error?.debugDescription == "Expected BinaryInteger at SELF, found nil")
+
+        error = #expect(throws: DecodingError.self) {
+            try KeyValueDecoder.decode([Int].self, from: [0, 1, true] as [Any])
+        }
+        #expect(error?.debugDescription == "Expected BinaryInteger at SELF[2], found Bool")
+
+        error = #expect(throws: DecodingError.self) {
+            try KeyValueDecoder.decode(AllTypes.self, from: ["tArray": [["tString": 0]]] as [String: Any])
+        }
+        #expect(error?.debugDescription == "Expected String at SELF.tArray[0].tString, found Int")
+
+        error = #expect(throws: DecodingError.self) {
+            try KeyValueDecoder.decode(AllTypes.self, from: ["tArray": [["tString": 0]]] as [String: Any])
+        }
+        #expect(error?.debugDescription == "Expected String at SELF.tArray[0].tString, found Int")
+    }
+#else
+    @Test()
     func decodingErrors() throws {
         expectDecodingError(try KeyValueDecoder.decode(Seafood.self, from: 10)) { error in
             #expect(error.debugDescription == "Expected String at SELF, found Int")
@@ -913,6 +953,7 @@ struct KeyValueDecoderTests {
             #expect(error.debugDescription == "Expected String at SELF.tArray[0].tString, found Int")
         }
     }
+#endif
 
     @Test
     func int_ClampsDoubles() {
@@ -997,6 +1038,7 @@ struct KeyValueDecoderTests {
     #endif
 }
 
+#if compiler(<6.1)
 func expectDecodingError<T>(_ expression: @autoclosure () throws -> T,
                             file: String = #filePath,
                             line: Int = #line,
@@ -1012,6 +1054,7 @@ func expectDecodingError<T>(_ expression: @autoclosure () throws -> T,
         Issue.record(error, "Expected DecodingError", sourceLocation: location)
     }
 }
+#endif
 
 extension DecodingError {