diff --git a/__tests__/index.test.ts b/__tests__/index.test.ts
index 853dc8c..1661485 100644
--- a/__tests__/index.test.ts
+++ b/__tests__/index.test.ts
@@ -16,6 +16,17 @@ test.each([
 });
 
 describe('#getExtension', () => {
+  it("should not throw an exception if `Oas` doesn't have an API definition", () => {
+    const oas = Oas.init(undefined);
+    expect(extensions.getExtension(extensions.SAMPLES_LANGUAGES, oas)).toHaveLength(5);
+  });
+
+  it("should not throw an exception if `Operation` doesn't have an API definition", () => {
+    const oas = Oas.init(undefined);
+    const operation = oas.operation('/pet', 'post');
+    expect(extensions.getExtension(extensions.SAMPLES_LANGUAGES, oas, operation)).toHaveLength(5);
+  });
+
   describe('oas-level extensions', () => {
     it('should use the default extension value if the extension is not present', () => {
       const oas = Oas.init(petstore);
@@ -43,6 +54,15 @@ describe('#getExtension', () => {
       const oas = Oas.init({ ...petstore, [`x-${extensions.EXPLORER_ENABLED}`]: false });
       expect(extensions.getExtension(extensions.EXPLORER_ENABLED, oas)).toBe(false);
     });
+
+    it('should not throw if `x-readme` is not an object', () => {
+      const oas = Oas.init({
+        ...petstore,
+        'x-readme': true,
+      });
+
+      expect(extensions.getExtension(extensions.SAMPLES_LANGUAGES, oas)).toHaveLength(5);
+    });
   });
 
   describe('operation-level', () => {
@@ -75,6 +95,13 @@ describe('#getExtension', () => {
 
       expect(extensions.getExtension(extensions.EXPLORER_ENABLED, oas, operation)).toBe(false);
     });
+
+    it('should not throw if `x-readme` is not an object', () => {
+      const operation = oas.operation('/pet', 'post');
+      operation.schema['x-readme'] = true;
+
+      expect(extensions.getExtension(extensions.SAMPLES_LANGUAGES, oas)).toHaveLength(5);
+    });
   });
 });
 
diff --git a/package-lock.json b/package-lock.json
index 0386902..07f7699 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -11769,9 +11769,9 @@
       "dev": true
     },
     "node_modules/oas": {
-      "version": "17.1.0",
-      "resolved": "https://registry.npmjs.org/oas/-/oas-17.1.0.tgz",
-      "integrity": "sha512-iaikb9s+xUi9AYqhak9nxX6H4lWUBEZ9FNQVzNb/N/lnD3Ue4dVYZ0ykMbdA+Rk0CK747RUJR4GH3j0HGJNIQQ==",
+      "version": "17.1.3",
+      "resolved": "https://registry.npmjs.org/oas/-/oas-17.1.3.tgz",
+      "integrity": "sha512-2N2Br8WbujxBCSFaNk10oRaYGM8ZTQAN6D4VMA/qAfpAbRWi+N3RdHsivjO9n2CX4XUwDjkqfzVy0RK/vVergw==",
       "peer": true,
       "dependencies": {
         "@apidevtools/json-schema-ref-parser": "^9.0.6",
@@ -23151,9 +23151,9 @@
       "dev": true
     },
     "oas": {
-      "version": "17.1.0",
-      "resolved": "https://registry.npmjs.org/oas/-/oas-17.1.0.tgz",
-      "integrity": "sha512-iaikb9s+xUi9AYqhak9nxX6H4lWUBEZ9FNQVzNb/N/lnD3Ue4dVYZ0ykMbdA+Rk0CK747RUJR4GH3j0HGJNIQQ==",
+      "version": "17.1.3",
+      "resolved": "https://registry.npmjs.org/oas/-/oas-17.1.3.tgz",
+      "integrity": "sha512-2N2Br8WbujxBCSFaNk10oRaYGM8ZTQAN6D4VMA/qAfpAbRWi+N3RdHsivjO9n2CX4XUwDjkqfzVy0RK/vVergw==",
       "peer": true,
       "requires": {
         "@apidevtools/json-schema-ref-parser": "^9.0.6",
diff --git a/src/index.ts b/src/index.ts
index e9e4604..86f2432 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -56,7 +56,7 @@ export function getExtension(extension: keyof Extensions, oas: Oas, operation?:
   if (operation) {
     if (operation.hasExtension('x-readme')) {
       const data = operation.getExtension('x-readme') as Extensions;
-      if (extension in data) {
+      if (data && typeof data === 'object' && extension in data) {
         return data[extension];
       }
     }
@@ -68,7 +68,7 @@ export function getExtension(extension: keyof Extensions, oas: Oas, operation?:
 
   if (oas.hasExtension('x-readme')) {
     const data = oas.getExtension('x-readme') as Extensions;
-    if (extension in data) {
+    if (data && typeof data === 'object' && extension in data) {
       return data[extension];
     }
   }