FollowBone - Disable rotation?

Hello, I’m using followbone to make an entity follow the player when he/she presses use on it, this is the code:

local bone = caller:LookupBone( "ValveBiped.Bip01_Pelvis" )

local knife = ents.Create("prop_physics")
knife:SetPos( caller:GetPos() + caller:GetAngles():Up() * 35 + caller:GetAngles():Forward() * 10 )
knife:SetAngles( caller:GetAngles() + Angle(90, 0, 0 ) )
knife:FollowBone( caller, bone )
knife:SetMoveType( MOVETYPE_NONE )
knife:SetSolid( SOLID_NONE )

But when the character moves the head/up down, the entity moves up and down as well. But I want it stay in one position and still follow the player.

I don’t think this is possible without you manually moving the entity you want bonemerged.