diff --git a/extra/html-extra/Tests/Fixtures/html_classes.test b/extra/html-extra/Tests/Fixtures/html_classes.test
index 65ecaba6ada..9b26d1564d8 100644
--- a/extra/html-extra/Tests/Fixtures/html_classes.test
+++ b/extra/html-extra/Tests/Fixtures/html_classes.test
@@ -4,9 +4,14 @@
 {{ html_classes('a', {'b': true, 'c': false}, 'd', false ? 'e', true ? 'f', '0') }}
 {% set class_a = 'a' %}
 {% set class_b = 'b' %}
-{{ html_classes(class_a, {(class_b): true})}}
+{%- set class_c -%}
+c
+{%- endset -%}
+{{ html_classes(class_a, { (class_b): true }) }}
+{{ html_classes(class_a, { (class_c): true }) }}
 --DATA--
 return []
 --EXPECT--
 a b d f 0
 a b
+a c