Fix build under OCaml 4.01.0
Fix build under OCaml 4.01.0

Reviewed By: @gabelevi

Differential Revision: D2084646

TiddoLangerak/flow,darioajr/flow,jdelStrother/flow,danvk/flow,shiftcars/flow,davidmason/flow,popham/flow,lyip1992/flow,samwgoldman/flow,jeffutter/flow,MichaelDeBoey/flow,mroch/flow,gabelevi/flow,Drooids/flow,Eyyub/flow,graue/flow,KevinTCoughlin/flow,KevinTCoughlin/flow,ForbesLindesay/flow,TiddoLangerak/flow,gabelevi/flow,JonathanUsername/flow,darioajr/flow,danvk/flow,Fresheyeball/flow,siddhartharay007/flow,darioajr/flow,mroch/flow,shiftcars/flow,JonathanUsername/flow,asivitz/flow,facebook/flow,cesarandreu/flow,mcanthony/flow-type,chenglou/flow,mroch/flow,nmote/flow,gabelevi/flow,paulshen/flow,paulshen/flow,jeffmo/flow,graue/flow,facebook/flow,Wanderfalke/flow,gabro/flow,JonathanUsername/flow,rafaelstz/flow,jgrund/flow,cesarandreu/flow,ForbesLindesay/flow,danvk/flow,JeckoHeroOrg/flow,AprilArcus/flow,claudiopro/flow,OCamlPro/flow,dv/flow,shiftcars/flow,JonathanUsername/flow,jamesgpearce/flow,facebook/flow,d14b3l/flow,asivitz/flow,paulshen/flow,mroch/flow,ylu1317/flow,lyip1992/flow,CJstar/flow,chenglou/flow,lyip1992/flow,OCamlPro/flow,ForbesLindesay/flow,mroch/flow,JohnyDays/flow,shiftcars/flow,YelaSeamless/flow,popham/flow,popham/flow,fletcherw/flow,JeckoHeroOrg/flow,KevinTCoughlin/flow,mroch/flow,rafaelstz/flow,CJstar/flow,popham/flow,jeffmo/flow,gabro/flow,jdelStrother/flow,YelaSeamless/flow,TiddoLangerak/flow,JohnyDays/flow,jamesgpearce/flow,YelaSeamless/flow,gabelevi/flow,davidmason/flow,popham/flow,popham/flow,jdelStrother/flow,jamesgpearce/flow,d14b3l/flow,samwgoldman/flow,jeffmo/flow,Wanderfalke/flow,jgrund/flow,JohnyDays/flow,ianobermiller/flow,davidmason/flow,ylu1317/flow,claudiopro/flow,Eyyub/flow,dv/flow,MichaelDeBoey/flow,davidmason/flow,fletcherw/flow,graue/flow,fletcherw/flow,jgrund/flow,JeckoHeroOrg/flow,CJstar/flow,jeffutter/flow,nmote/flow,siddhartharay007/flow,Wanderfalke/flow,JonathanUsername/flow,AprilArcus/flow,nmote/flow,siddhartharay007/flow,Fresheyeball/flow,samwgoldman/flow,Fresheyeball/flow,jdelStrother/flow,Fresheyeball/flow,samwgoldman/flow,d14b3l/flow,chenglou/flow,asivitz/flow,claudiopro/flow,gabro/flow,nmote/flow,jdelStrother/flow,mcanthony/flow-type,nmote/flow,samwgoldman/flow,d14b3l/flow,lyip1992/flow,davidmason/flow,jamesgpearce/flow,Jericho25/flow,paulshen/flow,chenglou/flow,ianobermiller/flow,mroch/flow,fletcherw/flow,ianobermiller/flow,matklad/flow,facebook/flow,jeffmo/flow,samwgoldman/flow,d14b3l/flow,chenglou/flow,cesarandreu/flow,gabro/flow,facebook/flow,claudiopro/flow,JeckoHeroOrg/flow,Wanderfalke/flow,nmote/flow,matklad/flow,shiftcars/flow,YelaSeamless/flow,gabelevi/flow,ianobermiller/flow,ylu1317/flow,asivitz/flow,JohnyDays/flow,facebook/flow,gabelevi/flow,YelaSeamless/flow,jamesgpearce/flow,Jericho25/flow,MichaelDeBoey/flow,jeffutter/flow,MichaelDeBoey/flow,jeffutter/flow,Drooids/flow,matklad/flow,ylu1317/flow,AprilArcus/flow,ylu1317/flow,jeffmo/flow,AgentME/flow,cesarandreu/flow,AgentME/flow,CJstar/flow,fletcherw/flow,facebook/flow,shiftcars/flow,rafaelstz/flow,Jericho25/flow,dv/flow,MichaelDeBoey/flow,gabelevi/flow,jdelStrother/flow,KevinTCoughlin/flow,jamesgpearce/flow,ForbesLindesay/flow,jamesgpearce/flow,TiddoLangerak/flow,mcanthony/flow-type,matklad/flow,JonathanUsername/flow,graue/flow,gabro/flow,AprilArcus/flow,matklad/flow,AgentME/flow,jeffmo/flow,JonathanUsername/flow,ForbesLindesay/flow,claudiopro/flow,darioajr/flow,fletcherw/flow,AgentME/flow,d14b3l/flow,gabro/flow,Eyyub/flow,Drooids/flow,OCamlPro/flow,jgrund/flow,AgentME/flow,dv/flow,siddhartharay007/flow,Eyyub/flow,jgrund/flow,popham/flow,ForbesLindesay/flow,graue/flow,AprilArcus/flow,AprilArcus/flow,rafaelstz/flow,chenglou/flow,graue/flow,jgrund/flow,Drooids/flow,rafaelstz/flow,mcanthony/flow-type,danvk/flow,samwgoldman/flow,nmote/flow,TiddoLangerak/flow,OCamlPro/flow,JeckoHeroOrg/flow