diff --git a/lib/internal/inspect-protocol.js b/lib/internal/inspect-protocol.js
index aeb60f2..75c6e0a 100644
--- a/lib/internal/inspect-protocol.js
+++ b/lib/internal/inspect-protocol.js
@@ -150,7 +150,7 @@ function decodeFrameHybi17(data) {
     default:
       // Nothing. We already have the right size.
   }
-  if ((dataAvailable - payloadOffset) < 0) return notComplete;
+  if ((dataAvailable - payloadOffset - payloadLength) < 0) return notComplete;
 
   const payloadEnd = payloadOffset + payloadLength;
   return {
@@ -175,17 +175,29 @@ class Client extends EventEmitter {
     this._unprocessed = Buffer.concat([this._unprocessed, chunk]);
 
     while (this._unprocessed.length > 2) {
-      const { closed, payload, rest } = decodeFrameHybi17(this._unprocessed);
+      const { closed, payload: payloadBuffer, rest } = decodeFrameHybi17(this._unprocessed);
       this._unprocessed = rest;
 
       if (closed) {
         this.reset();
         return;
       }
-      if (payload === null) break;
+      if (payloadBuffer === null) break;
+
+      const payloadStr = payloadBuffer.toString();
+      debuglog('< %s', payloadStr);
+      if (payloadStr[0] !== '{' || payloadStr[payloadStr.length - 1] !== '}') {
+        throw new Error(`Payload does not look like JSON: ${payloadStr}`);
+      }
+      let payload;
+      try {
+        payload = JSON.parse(payloadStr);
+      } catch (parseError) {
+        parseError.string = payloadStr;
+        throw parseError;
+      }
 
-      debuglog('< %s', payload);
-      const { id, method, params, result, error } = JSON.parse(payload.toString());
+      const { id, method, params, result, error } = payload;
       if (id) {
         const handler = this._pending[id];
         if (handler) {
@@ -196,7 +208,7 @@ class Client extends EventEmitter {
         this.emit('debugEvent', method, params);
         this.emit(method, params);
       } else {
-        throw new Error(`Unsupported response: ${payload.toString()}`);
+        throw new Error(`Unsupported response: ${payloadStr}`);
       }
     }
   }
diff --git a/test/cli/profile.test.js b/test/cli/profile.test.js
new file mode 100644
index 0000000..673b946
--- /dev/null
+++ b/test/cli/profile.test.js
@@ -0,0 +1,26 @@
+'use strict';
+const { test } = require('tap');
+
+const startCLI = require('./start-cli');
+
+test('profiles', (t) => {
+  const cli = startCLI(['examples/empty.js']);
+
+  function onFatal(error) {
+    cli.quit();
+    throw error;
+  }
+
+  return cli.waitFor(/break/)
+    .then(() => cli.waitForPrompt())
+    .then(() => cli.command('exec console.profile()'))
+    .then(() => {
+      t.match(cli.output, 'undefined');
+    })
+    .then(() => cli.command('exec console.profileEnd()'))
+    .then(() => {
+      t.match(cli.output, 'undefined');
+    })
+    .then(() => cli.quit())
+    .then(null, onFatal);
+});