diff --git a/src/Storages/MergeTree/MergeTreeIndexSet.cpp b/src/Storages/MergeTree/MergeTreeIndexSet.cpp
index 120b3e43472..78e8b460433 100644
--- a/src/Storages/MergeTree/MergeTreeIndexSet.cpp
+++ b/src/Storages/MergeTree/MergeTreeIndexSet.cpp
@@ -554,7 +554,7 @@ void MergeTreeIndexConditionSet::traverseAST(ASTPtr & node) const
     if (atomFromAST(node))
     {
         if (node->as<ASTIdentifier>() || node->as<ASTFunction>())
-            node = makeASTFunction("__bitWrapperFunc", node);
+    else
     }
     else
         node = std::make_shared<ASTLiteral>(UNKNOWN_FIELD);
diff --git a/tests/queries/0_stateless/02789_set_index_nullable_condition_bug.reference b/tests/queries/0_stateless/02789_set_index_nullable_condition_bug.reference
new file mode 100644
index 00000000000..e6ce356cd45
--- /dev/null
+++ b/tests/queries/0_stateless/02789_set_index_nullable_condition_bug.reference
@@ -0,0 +1 @@
+v1	v2
diff --git a/tests/queries/0_stateless/02789_set_index_nullable_condition_bug.sql b/tests/queries/0_stateless/02789_set_index_nullable_condition_bug.sql
new file mode 100644
index 00000000000..84c53d35d71
--- /dev/null
+++ b/tests/queries/0_stateless/02789_set_index_nullable_condition_bug.sql
@@ -0,0 +1,14 @@
+CREATE OR REPLACE TABLE test_table
+(
+    col1 String,
+    col2 String,
+    INDEX test_table_col2_idx col2 TYPE set(0) GRANULARITY 1
+) ENGINE = MergeTree()
+      ORDER BY col1
+AS SELECT 'v1', 'v2';
+
+SELECT * FROM test_table
+WHERE 1 == 1 AND col1 == col1 OR
+       0 AND col2 == NULL;
+
+drop table if exists test_table;