diff --git a/src/sparsematrix.jl b/src/sparsematrix.jl
index e4547cc7..76d82ea2 100644
--- a/src/sparsematrix.jl
+++ b/src/sparsematrix.jl
@@ -79,8 +79,8 @@ end
 
 size(S::SparseMatrixCSC) = (getfield(S, :m), getfield(S, :n))
 
-_goodbuffers(S::SparseMatrixCSC) = _goodbuffers(size(S)..., getcolptr(S), getrowval(S), nonzeros(S))
-_checkbuffers(S::SparseMatrixCSC) = (@assert _goodbuffers(S); S)
+_goodbuffers(S::AbstractSparseMatrixCSC) = _goodbuffers(size(S)..., getcolptr(S), getrowval(S), nonzeros(S))
+_checkbuffers(S::AbstractSparseMatrixCSC) = (@assert _goodbuffers(S); S)
 _checkbuffers(S::Union{Adjoint, Transpose}) = (_checkbuffers(parent(S)); S)
 
 function _goodbuffers(m, n, colptr, rowval, nzval)