Repro'd on GHC 7.8.1 and 7.6.3 Original code is: https://github.com/bitemyapp/bloodhound/ The code only works if I manually (out of band) run insertData (in a REPL) and then run main with the insertData invocation stripped out. If I run main with the insertData invocation included, it throws an exception (head) because the search results are empty. The behavior is as if queryTweet was executing after insertData deleted the index, but before it inserted the new data. The following is a stripped down example: insertData :: IO () insertData = do let encoded = encode exampleTweet _ <- deleteExampleIndex created <- createExampleIndex docCreated <- indexDocument (Server "http://localhost:9200") "twitter" "tweet" exampleTweet "1" print "test" return () el queryTweet :: IO (Either String Tweet) queryTweet = do let queryFilter = BoolFilter (MustMatch (Term "user" "bitemyapp") False) <||> IdentityFilter let search = Search Nothing (Just queryFilter) reply <- searchByIndex testServer "twitter" search let result = eitherDecode (responseBody reply) :: Either String (SearchResult Tweet) let myTweet = fmap (hitSource . head . hits . searchHits) result return myTweet main :: IO () main = do _ <- insertData myTweet <- queryTweet print myTweet further up the call chain, the http call is getting dispatched with http-conduit's gear, the result returned with the expression: withManager $ httpLbs req Included this in case it affects the semantics. Can anybody help? This has stumped me for a couple hours and I couldn't get anything clueful on IRC. Thanks to any that help. --- Chris