diff --git a/src/error/__tests__/GraphQLError-test.ts b/src/error/__tests__/GraphQLError-test.ts
index 2937038ffb..81dbf1fc71 100644
--- a/src/error/__tests__/GraphQLError-test.ts
+++ b/src/error/__tests__/GraphQLError-test.ts
@@ -144,6 +144,66 @@ describe('GraphQLError', () => {
     });
   });
 
+  it('defaults to original error extension only if extensions argument is not passed', () => {
+    class ErrorWithExtensions extends Error {
+      extensions: unknown;
+
+      constructor(message: string) {
+        super(message);
+        this.extensions = { original: 'extensions' };
+      }
+    }
+
+    const original = new ErrorWithExtensions('original');
+    const inheritedExtensions = new GraphQLError(
+      'InheritedExtensions',
+      undefined,
+      undefined,
+      undefined,
+      undefined,
+      original,
+      undefined,
+    );
+
+    expect(inheritedExtensions).to.deep.include({
+      message: 'InheritedExtensions',
+      originalError: original,
+      extensions: { original: 'extensions' },
+    });
+
+    const ownExtensions = new GraphQLError(
+      'OwnExtensions',
+      undefined,
+      undefined,
+      undefined,
+      undefined,
+      original,
+      { own: 'extensions' },
+    );
+
+    expect(ownExtensions).to.deep.include({
+      message: 'OwnExtensions',
+      originalError: original,
+      extensions: { own: 'extensions' },
+    });
+
+    const ownEmptyExtensions = new GraphQLError(
+      'OwnEmptyExtensions',
+      undefined,
+      undefined,
+      undefined,
+      undefined,
+      original,
+      {},
+    );
+
+    expect(ownEmptyExtensions).to.deep.include({
+      message: 'OwnEmptyExtensions',
+      originalError: original,
+      extensions: {},
+    });
+  });
+
   it('serializes to include all standard fields', () => {
     const eShort = new GraphQLError('msg');
     expect(JSON.stringify(eShort, null, 2)).to.equal(dedent`