diff --git a/jetty-websocket/websocket-common/src/main/java/org/eclipse/jetty/websocket/common/extensions/compress/ByteAccumulator.java b/jetty-websocket/websocket-common/src/main/java/org/eclipse/jetty/websocket/common/extensions/compress/ByteAccumulator.java
index aaca8301df2..14daae2d31e 100644
--- a/jetty-websocket/websocket-common/src/main/java/org/eclipse/jetty/websocket/common/extensions/compress/ByteAccumulator.java
+++ b/jetty-websocket/websocket-common/src/main/java/org/eclipse/jetty/websocket/common/extensions/compress/ByteAccumulator.java
@@ -40,7 +40,8 @@ public class ByteAccumulator
     {
         if (this.length + length > maxSize)
         {
-            throw new MessageTooLargeException("Frame is too large");
+            String err = String.format("Resulting message size [%,d] is too large for configured max of [%,d]", this.length + length, maxSize);
+            throw new MessageTooLargeException(err);
         }
 
         byte copy[] = new byte[length - offset];
diff --git a/jetty-websocket/websocket-common/src/test/java/org/eclipse/jetty/websocket/common/extensions/compress/ByteAccumulatorTest.java b/jetty-websocket/websocket-common/src/test/java/org/eclipse/jetty/websocket/common/extensions/compress/ByteAccumulatorTest.java
new file mode 100644
index 00000000000..e182eae2844
--- /dev/null
+++ b/jetty-websocket/websocket-common/src/test/java/org/eclipse/jetty/websocket/common/extensions/compress/ByteAccumulatorTest.java
@@ -0,0 +1,100 @@
+//
+//  ========================================================================
+//  Copyright (c) 1995-2018 Mort Bay Consulting Pty. Ltd.
+//  ------------------------------------------------------------------------
+//  All rights reserved. This program and the accompanying materials
+//  are made available under the terms of the Eclipse Public License v1.0
+//  and Apache License v2.0 which accompanies this distribution.
+//
+//      The Eclipse Public License is available at
+//      http://www.eclipse.org/legal/epl-v10.html
+//
+//      The Apache License v2.0 is available at
+//      http://www.opensource.org/licenses/apache2.0.php
+//
+//  You may elect to redistribute this code under either of these licenses.
+//  ========================================================================
+//
+
+package org.eclipse.jetty.websocket.common.extensions.compress;
+
+import static java.nio.charset.StandardCharsets.UTF_8;
+import static org.hamcrest.CoreMatchers.containsString;
+import static org.hamcrest.CoreMatchers.is;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+import java.nio.ByteBuffer;
+
+import org.eclipse.jetty.util.BufferUtil;
+import org.eclipse.jetty.websocket.api.MessageTooLargeException;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.ExpectedException;
+
+public class ByteAccumulatorTest
+{
+    @Rule
+    public ExpectedException expectedException = ExpectedException.none();
+
+    @Test
+    public void testCopyNormal()
+    {
+        ByteAccumulator accumulator = new ByteAccumulator(10_000);
+
+        byte hello[] = "Hello".getBytes(UTF_8);
+        byte space[] = " ".getBytes(UTF_8);
+        byte world[] = "World".getBytes(UTF_8);
+
+        accumulator.copyChunk(hello, 0, hello.length);
+        accumulator.copyChunk(space, 0, space.length);
+        accumulator.copyChunk(world, 0, world.length);
+
+        assertThat("Length", accumulator.getLength(), is(hello.length + space.length + world.length));
+
+        ByteBuffer out = ByteBuffer.allocate(200);
+        accumulator.transferTo(out);
+        String result = BufferUtil.toUTF8String(out);
+        assertThat("ByteBuffer to UTF8", result, is("Hello World"));
+    }
+
+    @Test
+    public void testTransferTo_NotEnoughSpace()
+    {
+        ByteAccumulator accumulator = new ByteAccumulator(10_000);
+
+        byte hello[] = "Hello".getBytes(UTF_8);
+        byte space[] = " ".getBytes(UTF_8);
+        byte world[] = "World".getBytes(UTF_8);
+
+        accumulator.copyChunk(hello, 0, hello.length);
+        accumulator.copyChunk(space, 0, space.length);
+        accumulator.copyChunk(world, 0, world.length);
+
+        int length = hello.length + space.length + world.length;
+        assertThat("Length", accumulator.getLength(), is(length));
+
+        ByteBuffer out = ByteBuffer.allocate(length - 2); // intentionally too small ByteBuffer
+        expectedException.expect(IllegalArgumentException.class);
+        expectedException.expectMessage(containsString("Not enough space in ByteBuffer"));
+        accumulator.transferTo(out);
+    }
+
+    @Test
+    public void testCopyChunk_NotEnoughSpace()
+    {
+
+        byte hello[] = "Hello".getBytes(UTF_8);
+        byte space[] = " ".getBytes(UTF_8);
+        byte world[] = "World".getBytes(UTF_8);
+
+        int length = hello.length + space.length + world.length;
+        ByteAccumulator accumulator = new ByteAccumulator(length - 2); // intentionally too small of a max
+
+        accumulator.copyChunk(hello, 0, hello.length);
+        accumulator.copyChunk(space, 0, space.length);
+
+        expectedException.expect(MessageTooLargeException.class);
+        expectedException.expectMessage(containsString("too large for configured max"));
+        accumulator.copyChunk(world, 0, world.length);
+    }
+}