diff --git a/src/core/components/operation-summary.jsx b/src/core/components/operation-summary.jsx
index 5eb40e3828aa5612832e54492c0444b3e06ab55b..bed0b3b4dea0e5e07fe1b8005830086d8a9ea116 100644
--- a/src/core/components/operation-summary.jsx
+++ b/src/core/components/operation-summary.jsx
@@ -2,6 +2,7 @@ import React, { PureComponent } from "react"
 import PropTypes from "prop-types"
 import { Iterable, List } from "immutable"
 import ImPropTypes from "react-immutable-proptypes"
+import toString from "lodash/toString"
 
 
 export default class OperationSummary extends PureComponent {
@@ -63,7 +64,7 @@ export default class OperationSummary extends PureComponent {
 
         {!showSummary ? null :
           <div className="opblock-summary-description">
-            {(resolvedSummary || summary).toString()}
+            {toString(resolvedSummary || summary)}
           </div>
         }
 
diff --git a/test/e2e-cypress/static/documents/bugs/5188.yaml b/test/e2e-cypress/static/documents/bugs/5188.yaml
index 814b95bb99273fe78a80e5c79345b8a926d78e1e..cb4d6205dabbf0bc71f14bb146fd62f13806b0b6 100644
--- a/test/e2e-cypress/static/documents/bugs/5188.yaml
+++ b/test/e2e-cypress/static/documents/bugs/5188.yaml
@@ -8,10 +8,17 @@ paths:
   /pet:
     get:
       tags:
-        - pet
+        - default
       summary: 
-        $ref: 
-      operationId: addPet
+        whatever: 123 
+      operationId: objectSummary
+      responses:
+        '405':
+          description: Invalid input
+    post:
+      tags:
+        - default
+      operationId: noSummary
       responses:
         '405':
           description: Invalid input
\ No newline at end of file
diff --git a/test/e2e-cypress/tests/bugs/5188.js b/test/e2e-cypress/tests/bugs/5188.js
index 80050bbf8581623706de5b85fc378f1b756834dd..b9c8f18cfb9ed6860435bee194007e5e611dd440 100644
--- a/test/e2e-cypress/tests/bugs/5188.js
+++ b/test/e2e-cypress/tests/bugs/5188.js
@@ -2,9 +2,17 @@ describe("#5188: non-string operation summary value", () => {
   it("should gracefully handle an object value for an operation summary", () => {
     cy
       .visit("?url=/documents/bugs/5188.yaml")
-      .get("#operations-pet-addPet")
+      .get("#operations-default-objectSummary")
       .click()
       .get(".opblock-summary-description")
       .contains("[object Object]")
-    })
+  })
+  it("should gracefully handle a missing value for an operation summary", () => {
+    cy
+      .visit("?url=/documents/bugs/5188.yaml")
+      .get("#operations-default-noSummary")
+      .click()
+      // check for response rendering; makes sure the Operation itself rendered
+      .contains("Invalid input")
+  })
 })