diff --git a/src/readonly.jl b/src/readonly.jl
index 00eacc3c..8031b91a 100644
--- a/src/readonly.jl
+++ b/src/readonly.jl
@@ -22,7 +22,7 @@ end
 
 Base.unsafe_convert(x::Type{Ptr{T}}, A::ReadOnly) where T = Base.unsafe_convert(x, parent(A))
 Base.elsize(::Type{ReadOnly{T,N,V}}) where {T,N,V} = Base.elsize(V)
-Base.@propagate_inbounds @inline Base.setindex!(x::ReadOnly, v, ind...) = if v == getindex(parent(x), ind...)
+Base.@propagate_inbounds @inline Base.setindex!(x::ReadOnly, v, ind::Vararg{Integer}) = if v == getindex(parent(x), ind...)
         v
     else
         error("Can't change $(typeof(x)).")