In general, in one aspect, a method includes receiving, by the one or more processors, from a client device, data specifying a query image, requesting, by the one or more processors, text labels responsive to the query image from a database of text labels associated with images, in response to no zero text labels that meet a threshold being returned for the request, sending, by the one or more processors, request data to the client device that causes the client device to display a prompt to enter a textual search query, receiving, in response to the request data, a textual search query from the client device, and in the database of text labels associated with images, associating, by the one or more processors, the textual search query with the query image. This and other embodiments of this aspect can include corresponding systems, apparatus, and computer program products.