diff --git a/lib/internal/assert/assertion_error.js b/lib/internal/assert/assertion_error.js
index dd1b911a4ba3e5..82dae694368c45 100644
--- a/lib/internal/assert/assertion_error.js
+++ b/lib/internal/assert/assertion_error.js
@@ -313,6 +313,16 @@ function createErrDiff(actual, expected, operator) {
   return `${msg}${skipped ? skippedMsg : ''}\n${res}${other}${end}${indicator}`;
 }
 
+function addEllipsis(string) {
+  const lines = StringPrototypeSplit(string, '\n');
+  if (lines.length > 10) {
+    lines.length = 10;
+    return `${ArrayPrototypeJoin(lines, '\n')}\n...`;
+  } else if (string.length > 512) {
+    return `${StringPrototypeSlice(string, 512)}...`;
+  }
+}
+
 class AssertionError extends Error {
   constructor(options) {
     validateObject(options, 'options');
@@ -467,16 +477,11 @@ class AssertionError extends Error {
     const tmpActual = this.actual;
     const tmpExpected = this.expected;
 
-    for (const name of ['actual', 'expected']) {
-      if (typeof this[name] === 'string') {
-        const lines = StringPrototypeSplit(this[name], '\n');
-        if (lines.length > 10) {
-          lines.length = 10;
-          this[name] = `${ArrayPrototypeJoin(lines, '\n')}\n...`;
-        } else if (this[name].length > 512) {
-          this[name] = `${StringPrototypeSlice(this[name], 512)}...`;
-        }
-      }
+    if (typeof this.actual === 'string') {
+      this.actual = addEllipsis(this.actual);
+    }
+    if (typeof this.expected === 'string') {
+      this.expected = addEllipsis(this.expected);
     }
 
     // This limits the `actual` and `expected` property default inspection to