diff --git a/unittests/conversion_to_bool.chai b/unittests/conversion_to_bool.chai
index d5512bf1..955b68ec 100644
--- a/unittests/conversion_to_bool.chai
+++ b/unittests/conversion_to_bool.chai
@@ -7,6 +7,12 @@ if (0) {
   assert_true(false);
 }
 
+if (!0) {
+  assert_true(true);
+} else {
+  assert_true(false);
+}
+
 while (0) {
   assert_true(false);
 }