stack overflow in reducer

trace.clj

ERROR - caught Throwable, no trap available, rethrowing
cascading.pipe.OperatorException: [803c4175-eb65-4168-bec...][cascalog.workflow$buffer$fn__572.invoke(workflow.clj:249)] operator Every failed executing operation: ClojureBuffer[decl:'?minhash-sig']
	at cascading.flow.stream.BufferEveryWindow.receive(BufferEveryWindow.java:139)
	at cascading.flow.stream.BufferEveryWindow.receive(BufferEveryWindow.java:41)
	at cascading.flow.hadoop.stream.HadoopGroupGate.run(HadoopGroupGate.java:90)
	at cascading.flow.hadoop.FlowReducer.reduce(FlowReducer.java:129)
	at org.apache.hadoop.mapred.ReduceTask.runOldReducer(ReduceTask.java:463)
	at org.apache.hadoop.mapred.ReduceTask.run(ReduceTask.java:411)
	at org.apache.hadoop.mapred.LocalJobRunner$Job.run(LocalJobRunner.java:215)
Caused by: java.lang.StackOverflowError
	at clojure.core$map$fn__3815.invoke(core.clj:2434)
	at clojure.lang.LazySeq.sval(LazySeq.java:42)
	at clojure.lang.LazySeq.seq(LazySeq.java:60)
	at clojure.lang.RT.seq(RT.java:466)
	at clojure.core$seq.invoke(core.clj:133)
	at clojure.core$map$fn__3815.invoke(core.clj:2435)
	at clojure.lang.LazySeq.sval(LazySeq.java:42)
	at clojure.lang.LazySeq.seq(LazySeq.java:60)
	at clojure.lang.RT.seq(RT.java:466)
	at clojure.core$seq.invoke(core.clj:133)
	at clojure.core$map$fn__3815.invoke(core.clj:2435)
	at clojure.lang.LazySeq.sval(LazySeq.java:42)
	at clojure.lang.LazySeq.seq(LazySeq.java:60)
	at clojure.lang.RT.seq(RT.java:466)
	at clojure.core$seq.invoke(core.clj:133)