diff --git a/src/java/org/apache/cassandra/utils/FastByteOperations.java b/src/java/org/apache/cassandra/utils/FastByteOperations.java
index b1514543d2..41f084d842 100644
--- a/src/java/org/apache/cassandra/utils/FastByteOperations.java
+++ b/src/java/org/apache/cassandra/utils/FastByteOperations.java
@@ -196,7 +196,6 @@ public class FastByteOperations
             {
                 BYTE_ARRAY_BASE_OFFSET = theUnsafe.arrayBaseOffset(byte[].class);
                 DIRECT_BUFFER_ADDRESS_OFFSET = theUnsafe.objectFieldOffset(Buffer.class.getDeclaredField("address"));
-
                 HEAP_HB_FIELD = theUnsafe.objectFieldOffset(ByteBuffer.class.getDeclaredField("hb"));
             }
             catch (Exception e)
@@ -276,8 +275,8 @@ public class FastByteOperations
             // Heap ByteBuffer (Mutable)
             if (srcBuf.hasArray() && !srcBuf.isReadOnly())
             {
-                src = theUnsafe.getObject(srcBuf, HEAP_HB_FIELD);
-                srcOffset = BYTE_ARRAY_BASE_OFFSET;
+                src = srcBuf.array();
+                srcOffset = BYTE_ARRAY_BASE_OFFSET + srcBuf.arrayOffset();
             }
             // Read-Only Heap ByteBuffer (Still has hb but read-only)
             else if (srcBuf.isReadOnly() && !srcBuf.isDirect())
diff --git a/test/unit/org/apache/cassandra/utils/Generators.java b/test/unit/org/apache/cassandra/utils/Generators.java
index 5f99421240..41f3d99f0d 100644
--- a/test/unit/org/apache/cassandra/utils/Generators.java
+++ b/test/unit/org/apache/cassandra/utils/Generators.java
@@ -365,7 +365,7 @@ public final class Generators
 
     public static Gen<ByteBuffer> bytes(int min, int max)
     {
-        return bytes(min, max, SourceDSL.arbitrary().constant(BBCases.HEAP));
+        return bytes(min, max, SourceDSL.arbitrary().pick(BBCases.HEAP, BBCases.READ_ONLY_HEAP));
     }
 
     public static Gen<ByteBuffer> directBytes(int min, int max)