diff --git a/src/style.cpp b/src/style.cpp
index 72927af..e82d524 100644
--- a/src/style.cpp
+++ b/src/style.cpp
@@ -35,6 +35,7 @@ static QVariant variant(const QJsonValue &val)
 		case QJsonValue::Bool:
 			return val.toVariant();
 		default:
+			qWarning() << val << ": invalid filter value";
 			return QVariant();
 	}
 }