diff --git a/src/monomial.jl b/src/monomial.jl
index 1872ef9..38d2465 100644
--- a/src/monomial.jl
+++ b/src/monomial.jl
@@ -164,8 +164,14 @@ end
 
 MP.variables(c::SA.AbstractCoefficients) = MP.variables(SA.keys(c))
 
+_lazy_collect(v::AbstractVector) = collect(v)
+_lazy_collect(v::Vector) = v
+
 function sparse_coefficients(p::MP.AbstractPolynomial)
-    return SA.SparseCoefficients(MP.monomials(p), MP.coefficients(p))
+    return SA.SparseCoefficients(
+        _lazy_collect(MP.monomials(p)),
+        _lazy_collect(MP.coefficients(p)),
+    )
 end
 
 function sparse_coefficients(t::MP.AbstractTermLike)
@@ -178,7 +184,7 @@ function MA.promote_operation(
 ) where {P<:MP.AbstractPolynomialLike}
     M = MP.monomial_type(P)
     T = MP.coefficient_type(P)
-    return SA.SparseCoefficients{M,T,MP.monomial_vector_type(M),Vector{T}}
+    return SA.SparseCoefficients{M,T,Vector{M},Vector{T}}
 end
 
 function algebra_element(p::MP.AbstractPolynomialLike)
diff --git a/test/runtests.jl b/test/runtests.jl
index 73e04f2..041149f 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -78,6 +78,10 @@ function api_test(B::Type{<:MB.AbstractMonomialIndexed}, degree)
     @test MB.algebra_element(MB.Polynomial{B}(const_mono)) + const_mono == 2
     @test iszero(const_mono - MB.algebra_element(MB.Polynomial{B}(const_mono)))
     @test iszero(MB.algebra_element(MB.Polynomial{B}(const_mono)) - const_mono)
+    @test typeof(MB.sparse_coefficients(sum(x))) ==
+          MA.promote_operation(MB.sparse_coefficients, typeof(sum(x)))
+    @test typeof(MB.algebra_element(sum(x))) ==
+          MA.promote_operation(MB.algebra_element, typeof(sum(x)))
 end
 
 function univ_orthogonal_test(