diff --git a/ydb/core/kqp/ut/pg/kqp_pg_ut.cpp b/ydb/core/kqp/ut/pg/kqp_pg_ut.cpp
index 72c95312fab6..bf610134fc81 100644
--- a/ydb/core/kqp/ut/pg/kqp_pg_ut.cpp
+++ b/ydb/core/kqp/ut/pg/kqp_pg_ut.cpp
@@ -4733,6 +4733,33 @@ Y_UNIT_TEST_SUITE(KqpPg) {
             UNIT_ASSERT_VALUES_EQUAL(ydbResults.begin()->Getcolumns().at(i).Getname(), colNames[i]);
         }
     }
+
+    Y_UNIT_TEST(LongDomainName) {
+        NKikimrConfig::TAppConfig appConfig;
+        appConfig.MutableTableServiceConfig()->SetEnablePreparedDdl(true);
+        auto setting = NKikimrKqp::TKqpSetting();
+        auto serverSettings = TKikimrSettings()
+            .SetAppConfig(appConfig)
+            .SetKqpSettings({setting})
+            .SetDomainRoot(std::string(65, 'a'));
+        TKikimrRunner kikimr(serverSettings.SetWithSampleTables(false));
+        auto db = kikimr.GetQueryClient();
+        auto settings = NYdb::NQuery::TExecuteQuerySettings().Syntax(NYdb::NQuery::ESyntax::Pg);
+        {
+            auto result = db.ExecuteQuery(R"(
+                CREATE TABLE t (id INT PRIMARY KEY, data1 UUID[]);
+            )", NYdb::NQuery::TTxControl::NoTx(), settings).ExtractValueSync();
+            UNIT_ASSERT_C(result.IsSuccess(), result.GetIssues().ToString());
+        }
+
+        {
+            const auto query = Q_(R"(
+                SELECT * FROM t;
+            )");
+            auto result = db.ExecuteQuery(query, NYdb::NQuery::TTxControl::BeginTx().CommitTx(), settings).ExtractValueSync();
+            UNIT_ASSERT_C(result.IsSuccess(), result.GetIssues().ToString());
+        }
+    }
 }
 
 } // namespace NKqp
diff --git a/ydb/library/yql/parser/pg_wrapper/syscache.cpp b/ydb/library/yql/parser/pg_wrapper/syscache.cpp
index 4dfc98bb1993..916fa6cc0519 100644
--- a/ydb/library/yql/parser/pg_wrapper/syscache.cpp
+++ b/ydb/library/yql/parser/pg_wrapper/syscache.cpp
@@ -696,10 +696,10 @@ namespace NMiniKQL {
 void PgCreateSysCacheEntries(void* ctx) {
     auto main = (TMainContext*)ctx;
     if (main->GUCSettings) {
-        if (main->GUCSettings->Get("ydb_database")) {
+        if (main->GUCSettings->Get("ydb_database") && main->GUCSettings->Get("ydb_database")->size() < NAMEDATALEN) {
             main->CurrentDatabaseName = NYql::TSysCache::MakePgDatabaseHeapTuple(NYql::PG_CURRENT_DATABASE_ID, main->GUCSettings->Get("ydb_database")->c_str());
         }
-        if (main->GUCSettings->Get("ydb_user")) {
+        if (main->GUCSettings->Get("ydb_user") && main->GUCSettings->Get("ydb_user")->size() < NAMEDATALEN) {
             main->CurrentUserName = NYql::TSysCache::MakePgRolesHeapTuple(NYql::PG_CURRENT_USER_ID, main->GUCSettings->Get("ydb_user")->c_str());
         }
     }