diff --git a/tests/queries/0_stateless/01778_test_LowCardinality_FixedString_pk.reference b/tests/queries/0_stateless/01778_test_LowCardinality_FixedString_pk.reference
new file mode 100644
index 00000000000..a134ce52c11
--- /dev/null
+++ b/tests/queries/0_stateless/01778_test_LowCardinality_FixedString_pk.reference
@@ -0,0 +1,3 @@
+100
+100
+100
diff --git a/tests/queries/0_stateless/01778_test_LowCardinality_FixedString_pk.sql b/tests/queries/0_stateless/01778_test_LowCardinality_FixedString_pk.sql
new file mode 100644
index 00000000000..1a0a1d35f76
--- /dev/null
+++ b/tests/queries/0_stateless/01778_test_LowCardinality_FixedString_pk.sql
@@ -0,0 +1,21 @@
+DROP TABLE IF EXISTS test_01778;
+
+CREATE TABLE test_01778
+(
+    `key` LowCardinality(FixedString(3)),
+    `d` date
+)
+ENGINE = MergeTree(d, key, 8192);
+
+
+INSERT INTO test_01778 SELECT toString(intDiv(number,8000)), today() FROM numbers(100000);
+INSERT INTO test_01778 SELECT toString('xxx'), today() FROM numbers(100);
+
+SELECT count() FROM test_01778 WHERE key = 'xxx';
+
+SELECT count() FROM test_01778 WHERE key = toFixedString('xxx', 3);
+
+SELECT count() FROM test_01778 WHERE toString(key) = 'xxx';
+
+DROP TABLE test_01778;
+