diff --git a/src/AbstractFixedEffectSolver.jl b/src/AbstractFixedEffectSolver.jl
index c90789c..07eb5e8 100644
--- a/src/AbstractFixedEffectSolver.jl
+++ b/src/AbstractFixedEffectSolver.jl
@@ -80,6 +80,9 @@ function solve_residuals!(r::AbstractVector{<:Real}, feM::AbstractFixedEffectSol
 end
 
 # A fallback method for collections of x
+# The container for data columns does not have to be a vector
+# This allows the use of iterators and tuples for xs in downstream packages
+# See https://github.com/FixedEffects/FixedEffects.jl/pull/65
 function solve_residuals!(xs, feM::AbstractFixedEffectSolver; progress_bar = true, kwargs...)
     iterations = Int[]
     convergeds = Bool[]