diff --git a/src/Physics/HeatConduction/heat_bc.jl b/src/Physics/HeatConduction/heat_bc.jl
index 35185cd4823c9f8f7da8ab6f5c61747891549380..9983809f3e155975b6c8ac919819cd4498b19279 100644
--- a/src/Physics/HeatConduction/heat_bc.jl
+++ b/src/Physics/HeatConduction/heat_bc.jl
@@ -12,7 +12,7 @@ struct TemperatureGradient{E,F} <: BoundaryProcess
 end
 BoundaryStyle(::Type{<:TemperatureGradient}) = Dirichlet()
 BoundaryStyle(::Type{<:TemperatureGradient{<:Damping}}) = Neumann()
-@inline boundaryvalue(bc::TemperatureGradient,l2,p2,s1,s2) where {F} = bc.T(s1.t)
+@inline boundaryvalue(bc::TemperatureGradient, l1, p2, l2, s1, s2) where {F} = bc.T(s1.t)
 
 @with_kw struct NFactor{W,S} <: BoundaryEffect
     winterfactor::W = Param(1.0, bounds=(0.0,1.0)) # applied when Tair <= 0