diff --git a/CHANGELOG.md b/CHANGELOG.md
index c6cf070a..cbcb51cc 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -72,6 +72,7 @@ After:
 - Add Snowflake specific implementation of `deduplicate()` ([#543](https://github.com/dbt-labs/dbt-utils/issues/543), [#548](https://github.com/dbt-labs/dbt-utils/pull/548))
 
 ## Fixes
+- Fix `union_relations` `source_column_name` none option.
 - Enable a negative part_number for `split_part()` ([#557](https://github.com/dbt-labs/dbt-utils/issues/557), [#559](https://github.com/dbt-labs/dbt-utils/pull/559))
 
 ## Quality of life
diff --git a/macros/sql/union.sql b/macros/sql/union.sql
index 13abd30d..e9a249a5 100644
--- a/macros/sql/union.sql
+++ b/macros/sql/union.sql
@@ -85,7 +85,7 @@
         (
             select
 
-                {%- if source_column_name != none %}
+                {%- if source_column_name is not none %}
                 cast({{ dbt_utils.string_literal(relation) }} as {{ type_string() }}) as {{ source_column_name }},
                 {%- endif %}