--- a/devtools/client/webconsole/new-console-output/components/message-types/EvaluationResult.js
+++ b/devtools/client/webconsole/new-console-output/components/message-types/EvaluationResult.js
@@ -54,17 +54,17 @@ function EvaluationResult(props) {
       && message.messageText.type === "longString"
     ) {
       messageBody = `${message.messageText.initial}…`;
     }
   } else {
     messageBody = GripMessageBody({
       dispatch,
       messageId,
-      grip: parameters,
+      grip: parameters[0],
       serviceContainer,
       useQuotes: true,
       escapeWhitespace: false,
       type,
       helperType,
     });
   }
 

--- a/devtools/client/webconsole/new-console-output/test/fixtures/stubs/evaluationResult.js
+++ b/devtools/client/webconsole/new-console-output/test/fixtures/stubs/evaluationResult.js
@@ -16,29 +16,31 @@ let stubPackets = new Map();
 stubPreparedMessages.set("new Date(0)", new ConsoleMessage({
   "id": "1",
   "allowRepeating": true,
   "source": "javascript",
   "timeStamp": 1479159921364,
   "type": "result",
   "helperType": null,
   "level": "log",
-  "parameters": {
-    "type": "object",
-    "actor": "server1.conn0.child1/obj30",
-    "class": "Date",
-    "extensible": true,
-    "frozen": false,
-    "sealed": false,
-    "ownPropertyLength": 0,
-    "preview": {
-      "timestamp": 0
+  "parameters": [
+    {
+      "type": "object",
+      "actor": "server1.conn0.child1/obj30",
+      "class": "Date",
+      "extensible": true,
+      "frozen": false,
+      "sealed": false,
+      "ownPropertyLength": 0,
+      "preview": {
+        "timestamp": 0
+      }
     }
-  },
-  "repeatId": "{\"frame\":null,\"groupId\":null,\"indent\":0,\"level\":\"log\",\"parameters\":{\"type\":\"object\",\"actor\":\"server1.conn0.child1/obj30\",\"class\":\"Date\",\"extensible\":true,\"frozen\":false,\"sealed\":false,\"ownPropertyLength\":0,\"preview\":{\"timestamp\":0}},\"source\":\"javascript\",\"type\":\"result\",\"userProvidedStyles\":null}",
+  ],
+  "repeatId": "{\"frame\":null,\"groupId\":null,\"indent\":0,\"level\":\"log\",\"parameters\":[{\"type\":\"object\",\"actor\":\"server1.conn0.child1/obj30\",\"class\":\"Date\",\"extensible\":true,\"frozen\":false,\"sealed\":false,\"ownPropertyLength\":0,\"preview\":{\"timestamp\":0}}],\"source\":\"javascript\",\"type\":\"result\",\"userProvidedStyles\":null}",
   "stacktrace": null,
   "frame": null,
   "groupId": null,
   "userProvidedStyles": null,
   "notes": null,
   "indent": 0
 }));
 
@@ -46,20 +48,22 @@ stubPreparedMessages.set("asdf()", new C
   "id": "1",
   "allowRepeating": true,
   "source": "javascript",
   "timeStamp": 1479159921377,
   "type": "result",
   "helperType": null,
   "level": "error",
   "messageText": "ReferenceError: asdf is not defined",
-  "parameters": {
-    "type": "undefined"
-  },
-  "repeatId": "{\"frame\":{\"source\":\"debugger eval code\",\"line\":1,\"column\":1},\"groupId\":null,\"indent\":0,\"level\":\"error\",\"messageText\":\"ReferenceError: asdf is not defined\",\"parameters\":{\"type\":\"undefined\"},\"source\":\"javascript\",\"type\":\"result\",\"userProvidedStyles\":null}",
+  "parameters": [
+    {
+      "type": "undefined"
+    }
+  ],
+  "repeatId": "{\"frame\":{\"source\":\"debugger eval code\",\"line\":1,\"column\":1},\"groupId\":null,\"indent\":0,\"level\":\"error\",\"messageText\":\"ReferenceError: asdf is not defined\",\"parameters\":[{\"type\":\"undefined\"}],\"source\":\"javascript\",\"type\":\"result\",\"userProvidedStyles\":null}",
   "stacktrace": null,
   "frame": {
     "source": "debugger eval code",
     "line": 1,
     "column": 1
   },
   "groupId": null,
   "exceptionDocURL": "https://developer.mozilla.org/docs/Web/JavaScript/Reference/Errors/Not_defined?utm_source=mozilla&utm_medium=firefox-console-errors&utm_campaign=default",
@@ -72,20 +76,22 @@ stubPreparedMessages.set("1 + @", new Co
   "id": "1",
   "allowRepeating": true,
   "source": "javascript",
   "timeStamp": 1479159921399,
   "type": "result",
   "helperType": null,
   "level": "error",
   "messageText": "SyntaxError: illegal character",
-  "parameters": {
-    "type": "undefined"
-  },
-  "repeatId": "{\"frame\":{\"source\":\"debugger eval code\",\"line\":1,\"column\":4},\"groupId\":null,\"indent\":0,\"level\":\"error\",\"messageText\":\"SyntaxError: illegal character\",\"parameters\":{\"type\":\"undefined\"},\"source\":\"javascript\",\"type\":\"result\",\"userProvidedStyles\":null}",
+  "parameters": [
+    {
+      "type": "undefined"
+    }
+  ],
+  "repeatId": "{\"frame\":{\"source\":\"debugger eval code\",\"line\":1,\"column\":4},\"groupId\":null,\"indent\":0,\"level\":\"error\",\"messageText\":\"SyntaxError: illegal character\",\"parameters\":[{\"type\":\"undefined\"}],\"source\":\"javascript\",\"type\":\"result\",\"userProvidedStyles\":null}",
   "stacktrace": null,
   "frame": {
     "source": "debugger eval code",
     "line": 1,
     "column": 4
   },
   "groupId": null,
   "exceptionDocURL": "https://developer.mozilla.org/docs/Web/JavaScript/Reference/Errors/Illegal_character?utm_source=mozilla&utm_medium=firefox-console-errors&utm_campaign=default",
@@ -97,41 +103,43 @@ stubPreparedMessages.set("1 + @", new Co
 stubPreparedMessages.set("inspect({a: 1})", new ConsoleMessage({
   "id": "1",
   "allowRepeating": true,
   "source": "javascript",
   "timeStamp": 1499776070751,
   "type": "result",
   "helperType": "inspectObject",
   "level": "log",
-  "parameters": {
-    "type": "object",
-    "actor": "server1.conn0.child1/obj35",
-    "class": "Object",
-    "extensible": true,
-    "frozen": false,
-    "sealed": false,
-    "ownPropertyLength": 1,
-    "preview": {
-      "kind": "Object",
-      "ownProperties": {
-        "a": {
-          "configurable": true,
-          "enumerable": true,
-          "writable": true,
-          "value": 1
-        }
-      },
-      "ownSymbols": [],
-      "ownPropertiesLength": 1,
-      "ownSymbolsLength": 0,
-      "safeGetterValues": {}
+  "parameters": [
+    {
+      "type": "object",
+      "actor": "server1.conn0.child1/obj35",
+      "class": "Object",
+      "extensible": true,
+      "frozen": false,
+      "sealed": false,
+      "ownPropertyLength": 1,
+      "preview": {
+        "kind": "Object",
+        "ownProperties": {
+          "a": {
+            "configurable": true,
+            "enumerable": true,
+            "writable": true,
+            "value": 1
+          }
+        },
+        "ownSymbols": [],
+        "ownPropertiesLength": 1,
+        "ownSymbolsLength": 0,
+        "safeGetterValues": {}
+      }
     }
-  },
-  "repeatId": "{\"frame\":null,\"groupId\":null,\"indent\":0,\"level\":\"log\",\"parameters\":{\"type\":\"object\",\"actor\":\"server1.conn0.child1/obj35\",\"class\":\"Object\",\"extensible\":true,\"frozen\":false,\"sealed\":false,\"ownPropertyLength\":1,\"preview\":{\"kind\":\"Object\",\"ownProperties\":{\"a\":{\"configurable\":true,\"enumerable\":true,\"writable\":true,\"value\":1}},\"ownSymbols\":[],\"ownPropertiesLength\":1,\"ownSymbolsLength\":0,\"safeGetterValues\":{}}},\"source\":\"javascript\",\"type\":\"result\",\"userProvidedStyles\":null}",
+  ],
+  "repeatId": "{\"frame\":null,\"groupId\":null,\"indent\":0,\"level\":\"log\",\"parameters\":[{\"type\":\"object\",\"actor\":\"server1.conn0.child1/obj35\",\"class\":\"Object\",\"extensible\":true,\"frozen\":false,\"sealed\":false,\"ownPropertyLength\":1,\"preview\":{\"kind\":\"Object\",\"ownProperties\":{\"a\":{\"configurable\":true,\"enumerable\":true,\"writable\":true,\"value\":1}},\"ownSymbols\":[],\"ownPropertiesLength\":1,\"ownSymbolsLength\":0,\"safeGetterValues\":{}}}],\"source\":\"javascript\",\"type\":\"result\",\"userProvidedStyles\":null}",
   "stacktrace": null,
   "frame": null,
   "groupId": null,
   "userProvidedStyles": null,
   "notes": null,
   "indent": 0
 }));
 
@@ -144,20 +152,22 @@ stubPreparedMessages.set("longString mes
   "helperType": null,
   "level": "error",
   "messageText": {
     "type": "longString",
     "initial": "Error: Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Lon",
     "length": 110007,
     "actor": "server1.conn0.child1/longString37"
   },
-  "parameters": {
-    "type": "undefined"
-  },
-  "repeatId": "{\"frame\":null,\"groupId\":null,\"indent\":0,\"level\":\"error\",\"messageText\":{\"type\":\"longString\",\"initial\":\"Error: Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Lon\",\"length\":110007,\"actor\":\"server1.conn0.child1/longString37\"},\"parameters\":{\"type\":\"undefined\"},\"source\":\"javascript\",\"type\":\"result\",\"userProvidedStyles\":null}",
+  "parameters": [
+    {
+      "type": "undefined"
+    }
+  ],
+  "repeatId": "{\"frame\":null,\"groupId\":null,\"indent\":0,\"level\":\"error\",\"messageText\":{\"type\":\"longString\",\"initial\":\"Error: Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Long error Lon\",\"length\":110007,\"actor\":\"server1.conn0.child1/longString37\"},\"parameters\":[{\"type\":\"undefined\"}],\"source\":\"javascript\",\"type\":\"result\",\"userProvidedStyles\":null}",
   "stacktrace": null,
   "frame": null,
   "groupId": null,
   "userProvidedStyles": null,
   "notes": null,
   "indent": 0
 }));
 

--- a/devtools/client/webconsole/new-console-output/test/store/release-actors.test.js
+++ b/devtools/client/webconsole/new-console-output/test/store/release-actors.test.js
@@ -37,29 +37,35 @@ describe("Release actor enhancer:", () =
       // Add a log message.
       dispatch(actions.messageAdd(
         stubPackets.get("console.log('myarray', ['red', 'green', 'blue'])")));
 
       let messages = getAllMessagesById(getState());
       const firstMessage = messages.first();
       const firstMessageActor = firstMessage.parameters[1].actor;
 
+      // Add an evaluation result message (see Bug 1408321).
+      const evaluationResultPacket = stubPackets.get("new Date(0)");
+      dispatch(actions.messageAdd(evaluationResultPacket));
+      const secondMessageActor = evaluationResultPacket.result.actor;
+
       const logCount = logLimit + 1;
       const packet = clonePacket(stubPackets.get(
         "console.assert(false, {message: 'foobar'})"));
-      const secondMessageActor = packet.message.arguments[0].actor;
+      const thirdMessageActor = packet.message.arguments[0].actor;
 
       for (let i = 1; i <= logCount; i++) {
         packet.message.arguments.push(`message num ${i}`);
         dispatch(actions.messageAdd(packet));
       }
 
-      expect(releasedActors.length).toBe(2);
+      expect(releasedActors.length).toBe(3);
       expect(releasedActors).toInclude(firstMessageActor);
       expect(releasedActors).toInclude(secondMessageActor);
+      expect(releasedActors).toInclude(thirdMessageActor);
     });
 
     it("properly releases backend actors after clear", () => {
       let releasedActors = [];
       const { dispatch, getState } = setupStore([], {
         proxy: {
           releaseActor: (actor) => {
             releasedActors.push(actor);
@@ -75,16 +81,23 @@ describe("Release actor enhancer:", () =
       const firstMessage = messages.first();
       const firstMessageActor = firstMessage.parameters[1].actor;
 
       const packet = clonePacket(stubPackets.get(
         "console.assert(false, {message: 'foobar'})"));
       const secondMessageActor = packet.message.arguments[0].actor;
       dispatch(actions.messageAdd(packet));
 
+      // Add an evaluation result message (see Bug 1408321).
+      const evaluationResultPacket = stubPackets.get("new Date(0)");
+      dispatch(actions.messageAdd(evaluationResultPacket));
+      const thirdMessageActor = evaluationResultPacket.result.actor;
+
+      // Kick-off the actor release.
       dispatch(actions.messagesClear());
 
-      expect(releasedActors.length).toBe(2);
+      expect(releasedActors.length).toBe(3);
       expect(releasedActors).toInclude(firstMessageActor);
       expect(releasedActors).toInclude(secondMessageActor);
+      expect(releasedActors).toInclude(thirdMessageActor);
     });
   });
 });

--- a/devtools/client/webconsole/new-console-output/utils/messages.js
+++ b/devtools/client/webconsole/new-console-output/utils/messages.js
@@ -247,28 +247,28 @@ function transformEvaluationResultPacket
     exceptionDocURL,
     frame,
     result,
     helperResult,
     timestamp: timeStamp,
     notes,
   } = packet;
 
-  let parameters = helperResult && helperResult.object
+  const parameter = helperResult && helperResult.object
     ? helperResult.object
     : result;
 
   const level = messageText ? MESSAGE_LEVEL.ERROR : MESSAGE_LEVEL.LOG;
   return new ConsoleMessage({
     source: MESSAGE_SOURCE.JAVASCRIPT,
     type: MESSAGE_TYPE.RESULT,
     helperType: helperResult ? helperResult.type : null,
     level,
     messageText,
-    parameters,
+    parameters: [parameter],
     exceptionDocURL,
     frame,
     timeStamp,
     notes,
   });
 }
 
 // Helpers