> db.foo.insert( { x : MinKey } )
> db.foo.find()
{ "_id" : ObjectId("4f3ad5dc7302cfae80686b02"), "x" : { $minKey : 1 } }
> db.foo.aggregate( { $project: { x : 1 } } )
{
	"errmsg" : "exception: assertion src/mongo/db/pipeline/value.cpp:183",
	"code" : 0,
	"ok" : 0
}

Tue Feb 14 16:46:11 [conn1]  local.foo Assertion failure false src/mongo/db/pipeline/value.cpp 183
0x100154641 0x10062a92d 0x100259696 0x100259b22 0x10019e356 0x10019e972 0x1006440d8 0x1006442e5 0x10024e55d 0x10014ba9c 0x1003d0a99 0x10030a804 0x10030d0f4 0x10030fa27 0x1001fb544 0x1001fd83f 0x1001d619e 0x1001dfbc6 0x1000206a4 0x100275c70 
 0   mongod                              0x0000000100154641 _ZN5mongo12sayDbContextEPKc + 161
 1   mongod                              0x000000010062a92d _ZN5mongo8assertedEPKcS1_j + 269
 2   mongod                              0x0000000100259696 _ZN5mongo5ValueC2EPNS_11BSONElementE + 1862
 3   mongod                              0x0000000100259b22 _ZN5mongo5Value21createFromBsonElementEPNS_11BSONElementE + 50
 4   mongod                              0x000000010019e356 _ZN5mongo8DocumentC2EPNS_7BSONObjE + 278
 5   mongod                              0x000000010019e972 _ZN5mongo8Document17createFromBsonObjEPNS_7BSONObjE + 50
 6   mongod                              0x00000001006440d8 _ZN5mongo20DocumentSourceCursor8findNextEv + 488
 7   mongod                              0x00000001006442e5 _ZN5mongo20DocumentSourceCursor3eofEv + 53
 8   mongod                              0x000000010024e55d _ZN5mongo21DocumentSourceProject3eofEv + 29
 9   mongod                              0x000000010014ba9c _ZN5mongo8Pipeline3runERNS_14BSONObjBuilderERSsRKN5boost13intrusive_ptrINS_14DocumentSourceEEE + 604
 10  mongod                              0x00000001003d0a99 _ZN5mongo15PipelineCommand3runERKSsRNS_7BSONObjEiRSsRNS_14BSONObjBuilderEb + 153
 11  mongod                              0x000000010030a804 _ZN5mongo12_execCommandEPNS_7CommandERKSsRNS_7BSONObjEiRNS_14BSONObjBuilderEb + 148
 12  mongod                              0x000000010030d0f4 _ZN5mongo11execCommandEPNS_7CommandERNS_6ClientEiPKcRNS_7BSONObjERNS_14BSONObjBuilderEb + 2148
 13  mongod                              0x000000010030fa27 _ZN5mongo12_runCommandsEPKcRNS_7BSONObjERNS_11_BufBuilderINS_16TrivialAllocatorEEERNS_14BSONObjBuilderEbi + 2359
 14  mongod                              0x00000001001fb544 _ZN5mongo11runCommandsEPKcRNS_7BSONObjERNS_5CurOpERNS_11_BufBuilderINS_16TrivialAllocatorEEERNS_14BSONObjBuilderEbi + 52
 15  mongod                              0x00000001001fd83f _ZN5mongo8runQueryERNS_7MessageERNS_12QueryMessageERNS_5CurOpES1_ + 3343
 16  mongod                              0x00000001001d619e _ZN5mongo13receivedQueryERNS_6ClientERNS_10DbResponseERNS_7MessageE + 654
 17  mongod                              0x00000001001dfbc6 _ZN5mongo16assembleResponseERNS_7MessageERNS_10DbResponseERKNS_11HostAndPortE + 870
 18  mongod                              0x00000001000206a4 _ZN5mongo16MyMessageHandler7processERNS_7MessageEPNS_21AbstractMessagingPortEPNS_9LastErrorE + 148
 19  mongod                              0x0000000100275c70 _ZN5mongo3pms9threadRunEPNS_13MessagingPortE + 768