diff --git a/HtmlExtension.php b/HtmlExtension.php
index e4cf9d3..266cbde 100644
--- a/HtmlExtension.php
+++ b/HtmlExtension.php
@@ -108,6 +108,6 @@ public static function htmlClasses(...$args): string
             }
         }
 
-        return implode(' ', array_unique($classes));
+        return implode(' ', array_unique(array_filter($classes, static function($v) { return '' !== $v; })));
     }
 }
diff --git a/Tests/Fixtures/html_classes.test b/Tests/Fixtures/html_classes.test
index 8a5304c..65ecaba 100644
--- a/Tests/Fixtures/html_classes.test
+++ b/Tests/Fixtures/html_classes.test
@@ -1,12 +1,12 @@
 --TEST--
 "html_classes" function
 --TEMPLATE--
-{{ html_classes('a', {'b': true, 'c': false}, 'd') }}
+{{ 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})}}
 --DATA--
 return []
 --EXPECT--
-a b d
+a b d f 0
 a b