diff --git a/packages/babel-plugin-proposal-class-properties/test/fixtures/private-loose/class-shadow-builtins/input.mjs b/packages/babel-plugin-proposal-class-properties/test/fixtures/private-loose/class-shadow-builtins/input.mjs
new file mode 100644
index 000000000000..924c4ec9897e
--- /dev/null
+++ b/packages/babel-plugin-proposal-class-properties/test/fixtures/private-loose/class-shadow-builtins/input.mjs
@@ -0,0 +1,3 @@
+export class TypeError {
+  #message
+}
diff --git a/packages/babel-plugin-proposal-class-properties/test/fixtures/private-loose/class-shadow-builtins/options.json b/packages/babel-plugin-proposal-class-properties/test/fixtures/private-loose/class-shadow-builtins/options.json
new file mode 100644
index 000000000000..59fe9f6a9225
--- /dev/null
+++ b/packages/babel-plugin-proposal-class-properties/test/fixtures/private-loose/class-shadow-builtins/options.json
@@ -0,0 +1,4 @@
+{
+  "plugins": ["proposal-class-properties"],
+  "externalHelpers": false
+}
diff --git a/packages/babel-plugin-proposal-class-properties/test/fixtures/private-loose/class-shadow-builtins/output.mjs b/packages/babel-plugin-proposal-class-properties/test/fixtures/private-loose/class-shadow-builtins/output.mjs
new file mode 100644
index 000000000000..3cbf7b8d3e93
--- /dev/null
+++ b/packages/babel-plugin-proposal-class-properties/test/fixtures/private-loose/class-shadow-builtins/output.mjs
@@ -0,0 +1,12 @@
+function _classPrivateFieldInitSpec(obj, privateMap, value) { _checkPrivateRedeclaration(obj, privateMap); privateMap.set(obj, value); }
+function _checkPrivateRedeclaration(obj, privateCollection) { if (privateCollection.has(obj)) { throw new TypeError("Cannot initialize the same private elements twice on an object"); } }
+var _message = /*#__PURE__*/new WeakMap();
+class _TypeError {
+  constructor() {
+    _classPrivateFieldInitSpec(this, _message, {
+      writable: true,
+      value: void 0
+    });
+  }
+}
+export { _TypeError as TypeError };
diff --git a/packages/babel-plugin-proposal-class-properties/test/fixtures/private/class-shadow-builtins/input.mjs b/packages/babel-plugin-proposal-class-properties/test/fixtures/private/class-shadow-builtins/input.mjs
new file mode 100644
index 000000000000..924c4ec9897e
--- /dev/null
+++ b/packages/babel-plugin-proposal-class-properties/test/fixtures/private/class-shadow-builtins/input.mjs
@@ -0,0 +1,3 @@
+export class TypeError {
+  #message
+}
diff --git a/packages/babel-plugin-proposal-class-properties/test/fixtures/private/class-shadow-builtins/options.json b/packages/babel-plugin-proposal-class-properties/test/fixtures/private/class-shadow-builtins/options.json
new file mode 100644
index 000000000000..59fe9f6a9225
--- /dev/null
+++ b/packages/babel-plugin-proposal-class-properties/test/fixtures/private/class-shadow-builtins/options.json
@@ -0,0 +1,4 @@
+{
+  "plugins": ["proposal-class-properties"],
+  "externalHelpers": false
+}
diff --git a/packages/babel-plugin-proposal-class-properties/test/fixtures/private/class-shadow-builtins/output.mjs b/packages/babel-plugin-proposal-class-properties/test/fixtures/private/class-shadow-builtins/output.mjs
new file mode 100644
index 000000000000..3cbf7b8d3e93
--- /dev/null
+++ b/packages/babel-plugin-proposal-class-properties/test/fixtures/private/class-shadow-builtins/output.mjs
@@ -0,0 +1,12 @@
+function _classPrivateFieldInitSpec(obj, privateMap, value) { _checkPrivateRedeclaration(obj, privateMap); privateMap.set(obj, value); }
+function _checkPrivateRedeclaration(obj, privateCollection) { if (privateCollection.has(obj)) { throw new TypeError("Cannot initialize the same private elements twice on an object"); } }
+var _message = /*#__PURE__*/new WeakMap();
+class _TypeError {
+  constructor() {
+    _classPrivateFieldInitSpec(this, _message, {
+      writable: true,
+      value: void 0
+    });
+  }
+}
+export { _TypeError as TypeError };
diff --git a/packages/babel-plugin-proposal-class-properties/test/fixtures/public-loose/class-shadow-builtins/input.mjs b/packages/babel-plugin-proposal-class-properties/test/fixtures/public-loose/class-shadow-builtins/input.mjs
new file mode 100644
index 000000000000..ed88dba1eea0
--- /dev/null
+++ b/packages/babel-plugin-proposal-class-properties/test/fixtures/public-loose/class-shadow-builtins/input.mjs
@@ -0,0 +1,3 @@
+export class TypeError {
+  message
+}
diff --git a/packages/babel-plugin-proposal-class-properties/test/fixtures/public-loose/class-shadow-builtins/options.json b/packages/babel-plugin-proposal-class-properties/test/fixtures/public-loose/class-shadow-builtins/options.json
new file mode 100644
index 000000000000..59fe9f6a9225
--- /dev/null
+++ b/packages/babel-plugin-proposal-class-properties/test/fixtures/public-loose/class-shadow-builtins/options.json
@@ -0,0 +1,4 @@
+{
+  "plugins": ["proposal-class-properties"],
+  "externalHelpers": false
+}
diff --git a/packages/babel-plugin-proposal-class-properties/test/fixtures/public-loose/class-shadow-builtins/output.mjs b/packages/babel-plugin-proposal-class-properties/test/fixtures/public-loose/class-shadow-builtins/output.mjs
new file mode 100644
index 000000000000..9debdcf55680
--- /dev/null
+++ b/packages/babel-plugin-proposal-class-properties/test/fixtures/public-loose/class-shadow-builtins/output.mjs
@@ -0,0 +1,9 @@
+function _defineProperty(obj, key, value) { key = _toPropertyKey(key); if (key in obj) { Object.defineProperty(obj, key, { value: value, enumerable: true, configurable: true, writable: true }); } else { obj[key] = value; } return obj; }
+function _toPropertyKey(arg) { var key = _toPrimitive(arg, "string"); return typeof key === "symbol" ? key : String(key); }
+function _toPrimitive(input, hint) { if (typeof input !== "object" || input === null) return input; var prim = input[Symbol.toPrimitive]; if (prim !== undefined) { var res = prim.call(input, hint || "default"); if (typeof res !== "object") return res; throw new TypeError("@@toPrimitive must return a primitive value."); } return (hint === "string" ? String : Number)(input); }
+class _TypeError {
+  constructor() {
+    _defineProperty(this, "message", void 0);
+  }
+}
+export { _TypeError as TypeError };
diff --git a/packages/babel-plugin-proposal-class-properties/test/fixtures/public/class-shadow-builtins/input.mjs b/packages/babel-plugin-proposal-class-properties/test/fixtures/public/class-shadow-builtins/input.mjs
new file mode 100644
index 000000000000..ed88dba1eea0
--- /dev/null
+++ b/packages/babel-plugin-proposal-class-properties/test/fixtures/public/class-shadow-builtins/input.mjs
@@ -0,0 +1,3 @@
+export class TypeError {
+  message
+}
diff --git a/packages/babel-plugin-proposal-class-properties/test/fixtures/public/class-shadow-builtins/options.json b/packages/babel-plugin-proposal-class-properties/test/fixtures/public/class-shadow-builtins/options.json
new file mode 100644
index 000000000000..59fe9f6a9225
--- /dev/null
+++ b/packages/babel-plugin-proposal-class-properties/test/fixtures/public/class-shadow-builtins/options.json
@@ -0,0 +1,4 @@
+{
+  "plugins": ["proposal-class-properties"],
+  "externalHelpers": false
+}
diff --git a/packages/babel-plugin-proposal-class-properties/test/fixtures/public/class-shadow-builtins/output.mjs b/packages/babel-plugin-proposal-class-properties/test/fixtures/public/class-shadow-builtins/output.mjs
new file mode 100644
index 000000000000..9debdcf55680
--- /dev/null
+++ b/packages/babel-plugin-proposal-class-properties/test/fixtures/public/class-shadow-builtins/output.mjs
@@ -0,0 +1,9 @@
+function _defineProperty(obj, key, value) { key = _toPropertyKey(key); if (key in obj) { Object.defineProperty(obj, key, { value: value, enumerable: true, configurable: true, writable: true }); } else { obj[key] = value; } return obj; }
+function _toPropertyKey(arg) { var key = _toPrimitive(arg, "string"); return typeof key === "symbol" ? key : String(key); }
+function _toPrimitive(input, hint) { if (typeof input !== "object" || input === null) return input; var prim = input[Symbol.toPrimitive]; if (prim !== undefined) { var res = prim.call(input, hint || "default"); if (typeof res !== "object") return res; throw new TypeError("@@toPrimitive must return a primitive value."); } return (hint === "string" ? String : Number)(input); }
+class _TypeError {
+  constructor() {
+    _defineProperty(this, "message", void 0);
+  }
+}
+export { _TypeError as TypeError };
diff --git a/packages/babel-traverse/src/path/modification.ts b/packages/babel-traverse/src/path/modification.ts
index 3da582b72f43..bbf90e5e5837 100644
--- a/packages/babel-traverse/src/path/modification.ts
+++ b/packages/babel-traverse/src/path/modification.ts
@@ -13,6 +13,7 @@ import {
   expressionStatement,
   isAssignmentExpression,
   isCallExpression,
+  isExportNamedDeclaration,
   isExpression,
   isIdentifier,
   isSequenceExpression,
@@ -34,12 +35,19 @@ export function insertBefore(
 
   const nodes = this._verifyNodeList(nodes_);
 
-  const { parentPath } = this;
+  const { parentPath, parent } = this;
 
   if (
     parentPath.isExpressionStatement() ||
     parentPath.isLabeledStatement() ||
-    parentPath.isExportNamedDeclaration() ||
+    // https://github.com/babel/babel/issues/15293
+    // When Babel transforms `export class String { field }`, the class properties plugin will inject the defineProperty
+    // helper, which depends on the builtins e.g. String, Number, Symbol, etc. To prevent them from being shadowed by local
+    // exports, the helper injector replaces the named export into `class _String { field }; export { _String as String }`,
+    // with `parentPath` here changed to the moved ClassDeclaration, causing rare inconsistency between `parent` and `parentPath`.
+    // Here we retrieve the parent type from the `parent` property. This is a temporary fix and we should revisit when
+    // helpers should get injected.
+    isExportNamedDeclaration(parent) ||
     (parentPath.isExportDefaultDeclaration() && this.isDeclaration())
   ) {
     return parentPath.insertBefore(nodes);
@@ -169,11 +177,12 @@ export function insertAfter(
 
   const nodes = this._verifyNodeList(nodes_);
 
-  const { parentPath } = this;
+  const { parentPath, parent } = this;
   if (
     parentPath.isExpressionStatement() ||
     parentPath.isLabeledStatement() ||
-    parentPath.isExportNamedDeclaration() ||
+    // see insertBefore
+    isExportNamedDeclaration(parent) ||
     (parentPath.isExportDefaultDeclaration() && this.isDeclaration())
   ) {
     return parentPath.insertAfter(