diff --git a/src/Interface.jl b/src/Interface.jl
index 6241657a..a9e4a71d 100644
--- a/src/Interface.jl
+++ b/src/Interface.jl
@@ -468,7 +468,7 @@ function FragmentBasedReactiveFilmGrowthInterfaceConstantT(domainfilm, domain2,
     Gpart = ArrayPartition(domainfilm.Gs,domain2.Gs)
     dGrxns = -M*Gpart
     kfs = getkf.(reactions,nothing,T,0.0,0.0,Ref([]),0.0,0.0,dGrxns,0.0)
-    Kc = getKcs(domain1.phase,domain2.phase,T,Nrp1,Nrp2,dGrxns)
+    Kc = getKcs(domainfilm.phase,domain2.phase,T,Nrp1,Nrp2,dGrxns)
     krevs = kfs./Kc
 
     M, Nrp1, Nrp2 = getstoichmatrix(domainfilm, domain2, reactions)