IN predicate against a materialized/temp table index without an order by returns wrong results

select srid, proj4text from spatial_ref_sys where srid in (3875,4326);
 srid |                                                   proj4text                                                    
------+----------------------------------------------------------------------------------------------------------------
 3875 | +proj=tmerc +lat_0=0 +lon_0=21 +k=1 +x_0=21500000 +y_0=0 +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs
 4326 | +proj=longlat +datum=WGS84 +no_defs
(2 rows)

select srid, proj4text from spatial_ref_sys where srid in (4326,3875);
 srid |              proj4text              
------+-------------------------------------
 4326 | +proj=longlat +datum=WGS84 +no_defs
(1 row)