diff --git a/pglablib/PgDatabaseCatalog.cpp b/pglablib/PgDatabaseCatalog.cpp
index ab012f5..10e0903 100644
--- a/pglablib/PgDatabaseCatalog.cpp
+++ b/pglablib/PgDatabaseCatalog.cpp
@@ -75,8 +75,15 @@ QString getTablespaceDisplayString(const PgDatabaseCatalog &cat, Oid oid)
 
 QString getTypeDisplayString(const PgDatabaseCatalog &cat, Oid oid, int32_t typmod)
 {
+	if (oid == 0) {
+		return QString();
+	}
+
 	auto tc = cat.types();
 	auto t = tc->getByKey(oid);
+	if (t.oid == InvalidOid) {
+		return "(invalid/unknown)";
+	}
 	QString s;
 	if (t.category == TypCategory::Array) {
 //		auto et = tc->getByKey(t.elem);