diff --git a/Tests/CryptoTests/Digests/DigestsTests.swift b/Tests/CryptoTests/Digests/DigestsTests.swift
index 7eb02cf7..e706af44 100644
--- a/Tests/CryptoTests/Digests/DigestsTests.swift
+++ b/Tests/CryptoTests/Digests/DigestsTests.swift
@@ -113,6 +113,7 @@ class DigestsTests: XCTestCase {
         try orFail { try testHashFunctionImplementsCoW(hf: SHA512.self) }
     }
     
+    @available(macOS 10.15, iOS 13.2, tvOS 13.2, watchOS 6.1, *)
     func testBlockSizes() {
         XCTAssertEqual(Insecure.MD5.blockByteCount, 64)
         XCTAssertEqual(Insecure.SHA1.blockByteCount, 64)
diff --git a/Tests/_CryptoExtrasTests/Utils/BytesUtil.swift b/Tests/_CryptoExtrasTests/Utils/BytesUtil.swift
index e87e2e2d..a01b0db9 100644
--- a/Tests/_CryptoExtrasTests/Utils/BytesUtil.swift
+++ b/Tests/_CryptoExtrasTests/Utils/BytesUtil.swift
@@ -60,7 +60,7 @@ extension DataProtocol {
     var hexString: String {
         get {
             let hexLen = self.count * 2
-            return String.init(unsafeUninitializedCapacity: hexLen) { buf in
+            let bytes = Array(unsafeUninitializedCapacity: hexLen) { buf, count in
                 var offset = 0
 
                 self.regions.forEach { (_) in
@@ -70,8 +70,9 @@ extension DataProtocol {
                         offset += 1
                     }
                 }
-                return offset
+                count = offset
             }
+            return String(decoding: bytes, as: UTF8.self)
         }
     }
 }