diff --git a/database/postgis/fields.go b/database/postgis/fields.go
index 011bbdf..9383661 100644
--- a/database/postgis/fields.go
+++ b/database/postgis/fields.go
@@ -60,6 +60,10 @@ type validatedGeometryType struct {
 }
 
 func (t *validatedGeometryType) GeneralizeSql(colSpec *ColumnSpec, spec *GeneralizedTableSpec) string {
+	if spec.Source.GeometryType != "polygon" {
+		// TODO return warning earlier
+		log.Warnf("validated_geometry column returns polygon geometries for %s", spec.FullName)
+	}
 	return fmt.Sprintf(`ST_Buffer(ST_SimplifyPreserveTopology("%s", %f), 0) as "%s"`,
 		colSpec.Name, spec.Tolerance, colSpec.Name,
 	)