diff --git a/src/transform/astHelpers.ts b/src/transform/astHelpers.ts
index 9c56a09..42c4903 100644
--- a/src/transform/astHelpers.ts
+++ b/src/transform/astHelpers.ts
@@ -118,6 +118,8 @@ export function convertExpression(node: ts.Expression): ESTree.Expression {
   }
   if (ts.isIdentifier(node)) {
     return createIdentifier(node);
+  } else if (node.kind == ts.SyntaxKind.NullKeyword) {
+    return { type: "Literal", value: null };
   } else {
     throw new UnsupportedSyntaxError(node);
   }
diff --git a/tests/testcases/issue-189/expected.d.ts b/tests/testcases/issue-189/expected.d.ts
new file mode 100644
index 0000000..13e00eb
--- /dev/null
+++ b/tests/testcases/issue-189/expected.d.ts
@@ -0,0 +1,2 @@
+declare class MyClass extends null {}
+export { MyClass };
diff --git a/tests/testcases/issue-189/index.d.ts b/tests/testcases/issue-189/index.d.ts
new file mode 100644
index 0000000..26eb14e
--- /dev/null
+++ b/tests/testcases/issue-189/index.d.ts
@@ -0,0 +1 @@
+export class MyClass extends null {}