diff --git a/src/main/java/io/netty/buffer/api/BufferHolder.java b/src/main/java/io/netty/buffer/api/BufferHolder.java
index 6a1f6db..e17600d 100644
--- a/src/main/java/io/netty/buffer/api/BufferHolder.java
+++ b/src/main/java/io/netty/buffer/api/BufferHolder.java
@@ -78,11 +78,6 @@ public abstract class BufferHolder<T extends BufferHolder<T>> implements Rc<T> {
         return buf.isOwned();
     }
 
-    @Override
-    public int countBorrows() {
-        return buf.countBorrows();
-    }
-
     @SuppressWarnings("unchecked")
     @Override
     public Send<T> send() {
diff --git a/src/main/java/io/netty/buffer/api/Rc.java b/src/main/java/io/netty/buffer/api/Rc.java
index 6ec164e..48d776a 100644
--- a/src/main/java/io/netty/buffer/api/Rc.java
+++ b/src/main/java/io/netty/buffer/api/Rc.java
@@ -69,15 +69,6 @@ public interface Rc<I extends Rc<I>> extends AutoCloseable {
      */
     boolean isOwned();
 
-    /**
-     * Count the number of borrows of this object.
-     * Note that even if the number of borrows is {@code 0}, this object might not be {@linkplain #isOwned() owned}
-     * because there could be other restrictions involved in ownership.
-     *
-     * @return The number of borrows, if any, of this object.
-     */
-    int countBorrows();
-
     /**
      * Check if this object is accessible.
      *
diff --git a/src/main/java/io/netty/buffer/api/RcSupport.java b/src/main/java/io/netty/buffer/api/RcSupport.java
index 99a4310..6448adc 100644
--- a/src/main/java/io/netty/buffer/api/RcSupport.java
+++ b/src/main/java/io/netty/buffer/api/RcSupport.java
@@ -106,7 +106,13 @@ public abstract class RcSupport<I extends Rc<I>, T extends RcSupport<I, T>> impl
         return acquires == 0;
     }
 
-    @Override
+    /**
+     * Count the number of borrows of this object.
+     * Note that even if the number of borrows is {@code 0}, this object might not be {@linkplain #isOwned() owned}
+     * because there could be other restrictions involved in ownership.
+     *
+     * @return The number of borrows, if any, of this object.
+     */
     public int countBorrows() {
         return Math.max(acquires, 0);
     }
diff --git a/src/main/java/io/netty/buffer/api/adaptor/ByteBufAdaptor.java b/src/main/java/io/netty/buffer/api/adaptor/ByteBufAdaptor.java
index fa0ec00..619e0ff 100644
--- a/src/main/java/io/netty/buffer/api/adaptor/ByteBufAdaptor.java
+++ b/src/main/java/io/netty/buffer/api/adaptor/ByteBufAdaptor.java
@@ -24,6 +24,7 @@ import io.netty.buffer.SlicedByteBuf;
 import io.netty.buffer.Unpooled;
 import io.netty.buffer.api.Buffer;
 import io.netty.buffer.api.BufferAllocator;
+import io.netty.buffer.api.RcSupport;
 import io.netty.util.ByteProcessor;
 import io.netty.util.IllegalReferenceCountException;
 
@@ -212,13 +213,13 @@ public final class ByteBufAdaptor extends ByteBuf {
     public ByteBuf ensureWritable(int minWritableBytes) {
         checkAccess();
         if (writableBytes() < minWritableBytes) {
-            int borrows = buffer.countBorrows();
             try {
-                if (borrows == 0) {
+                if (buffer.isOwned()) {
                     // Good place.
                     buffer.ensureWritable(minWritableBytes);
                 } else {
                     // Highly questionable place, but ByteBuf technically allows this, so we have to emulate.
+                    int borrows = countBorrows();
                     release(borrows);
                     try {
                         buffer.ensureWritable(minWritableBytes);
@@ -1650,7 +1651,18 @@ public final class ByteBufAdaptor extends ByteBuf {
 
     @Override
     public int refCnt() {
-        return buffer.isAccessible()? 1 + buffer.countBorrows() : 0;
+        return 1 + countBorrows();
+    }
+
+    private int countBorrows() {
+        if (!buffer.isAccessible()) {
+            return -1;
+        }
+        if (buffer instanceof RcSupport) {
+            var rc = (RcSupport<?, ?>) buffer;
+            return rc.countBorrows();
+        }
+        return buffer.isOwned()? 0 : 1;
     }
 
     @Override