postgres crash on CURSORS

I have found I can crash the backend with the following queries:
test=> BEGIN WORK;BEGINtest=> DECLARE bigtable_cursor CURSOR FORtest-> SELECT * FROM bigtable;SELECTtest=> FETCH 3
priorFROM bigtable_cursor;ERROR:  parser: parse error at or near "prior"test=> FETCH prior FROM
bigtable_cursor;pqReadData()-- backend closed the channel unexpectedly.        This probably means the backend
terminatedabnormally        before or while processing the request.The connection to the server was lost. Attempting
reset:Succeeded.
 

Here is the backtrace.  Comments?

---------------------------------------------------------------------------


#0  0x281d2d65 in kill ()
#1  0x2821ea5d in abort ()
#2  0x8146548 in ExcAbort (excP=0x8199294, detail=0, data=0x0,    message=0x81812ad "!(MyProc->xmin != 0)") at
excabort.c:27
#3  0x8146497 in ExcUnCaught (excP=0x8199294, detail=0, data=0x0,    message=0x81812ad "!(MyProc->xmin != 0)") at
exc.c:170
#4  0x81464ef in ExcRaise (excP=0x8199294, detail=0, data=0x0,    message=0x81812ad "!(MyProc->xmin != 0)") at
exc.c:187
#5  0x8145b3a in ExceptionalCondition (   conditionName=0x81812ad "!(MyProc->xmin != 0)", exceptionP=0x8199294,
detail=0x0,fileName=0x81811a3 "sinval.c", lineNumber=362) at assert.c:73
 
#6  0x8103730 in GetSnapshotData (serializable=0 '\000') at sinval.c:362
#7  0x81501d7 in SetQuerySnapshot () at tqual.c:611
#8  0x810c329 in pg_exec_query_dest (   query_string=0x81cd398 "FETCH prior FROM bigtable_cursor;\n", dest=Debug,
aclOverride=0)at postgres.c:677
 
#9  0x810c244 in pg_exec_query (   query_string=0x81cd398 "FETCH prior FROM bigtable_cursor;\n")   at postgres.c:607
#10 0x810d43d in PostgresMain (argc=4, argv=0x8047534, real_argc=4,    real_argv=0x8047534) at postgres.c:1642
#11 0x80c07fc in main (argc=4, argv=0x8047534) at main.c:103
#12 0x8062a9c in __start ()

--  Bruce Momjian                        |  http://www.op.net/~candle pgman@candle.pha.pa.us               |  (610)
853-3000+  If your life is a hard drive,     |  830 Blythe Avenue +  Christ can be your backup.        |  Drexel Hill,
Pennsylvania19026