diff --git a/app/astride/sandbox.js b/app/astride/sandbox.js
index daa2952..342ce1f 100644
--- a/app/astride/sandbox.js
+++ b/app/astride/sandbox.js
@@ -294,10 +294,14 @@ export default class Sandbox {
         if (test.yield) {
           return test;
         }
+        result = {
+          yield: YIELD_NONE,
+          value: undefined,
+        };
         if (test.value) {
           result = this.executeSync(node.consequent, depth + 1);
         }
-        else {
+        else if (node.alternate) {
           result = this.executeSync(node.alternate, depth + 1);
         }
         if (result.yield) {
diff --git a/app/astride/sandbox.test.js b/app/astride/sandbox.test.js
index 6a5e335..5914443 100644
--- a/app/astride/sandbox.test.js
+++ b/app/astride/sandbox.test.js
@@ -135,6 +135,9 @@ test('evaluates conditional branches', async () => {
       else {
         bar = 2;
       }
+      if (await false) {
+        bar = 1;
+      }
     `),
   );
   await finish(sandbox);