diff --git a/src/sparsematrix.jl b/src/sparsematrix.jl
index fced1b28..56ee216a 100644
--- a/src/sparsematrix.jl
+++ b/src/sparsematrix.jl
@@ -2402,7 +2402,7 @@ function Base.reducedim_initarray(A::AbstractSparseMatrixCSC, region, v0, ::Type
 end
 
 # General mapreduce
-function _mapreducezeros(f, op, ::Type{T}, nzeros::Integer, v0) where T
+function _mapreducezeros(f::F, op::G, ::Type{T}, nzeros::Integer, v0) where {F,G,T}
     nzeros == 0 && return v0
 
     # Reduce over first zero
@@ -2421,7 +2421,7 @@ function _mapreducezeros(f, op, ::Type{T}, nzeros::Integer, v0) where T
     v
 end
 
-function Base._mapreduce(f, op, ::Base.IndexCartesian, A::AbstractSparseMatrixCSC{T}) where T
+function Base._mapreduce(f::F, op::G, ::Base.IndexCartesian, A::AbstractSparseMatrixCSC{T}) where {F,G,T}
     z = nnz(A)
     n = widelength(A)
     if z == 0
@@ -2436,11 +2436,11 @@ function Base._mapreduce(f, op, ::Base.IndexCartesian, A::AbstractSparseMatrixCS
 end
 
 # Specialized mapreduce for +/*/min/max/_extrema_rf
-_mapreducezeros(f, op::Union{typeof(Base.add_sum),typeof(+)}, ::Type{T}, nzeros::Integer, v0) where {T} =
+_mapreducezeros(f::F, op::Union{typeof(Base.add_sum),typeof(+)}, ::Type{T}, nzeros::Integer, v0) where {F,T} =
     nzeros == 0 ? op(zero(v0), v0) : op(f(zero(T))*nzeros, v0)
-_mapreducezeros(f, op::Union{typeof(Base.mul_prod),typeof(*)},::Type{T}, nzeros::Integer, v0) where {T} =
+_mapreducezeros(f::F, op::Union{typeof(Base.mul_prod),typeof(*)},::Type{T}, nzeros::Integer, v0) where {F,T} =
     nzeros == 0 ? op(one(v0), v0) : op(f(zero(T))^nzeros, v0)
-_mapreducezeros(f, op::Union{typeof(min),typeof(max)}, ::Type{T}, nzeros::Integer, v0) where {T} =
+_mapreducezeros(f::F, op::Union{typeof(min),typeof(max)}, ::Type{T}, nzeros::Integer, v0) where {F,T} =
     nzeros == 0 ? v0 : op(v0, f(zero(T)))
 _mapreducezeros(f::Base.ExtremaMap, op::typeof(Base._extrema_rf), ::Type{T}, nzeros::Integer, v0) where {T} =
     nzeros == 0 ? v0 : op(v0, f(zero(T)))
@@ -2451,7 +2451,7 @@ Base._any(f, A::AbstractSparseMatrixCSC, ::Colon) =
 Base._all(f, A::AbstractSparseMatrixCSC, ::Colon) =
     iszero(widelength(A)) ? true  : Base._mapreduce(f, &, IndexCartesian(), A)
 
-function Base._mapreduce(f, op::Union{typeof(Base.mul_prod),typeof(*)}, ::Base.IndexCartesian, A::AbstractSparseMatrixCSC{T}) where T
+function Base._mapreduce(f::F, op::Union{typeof(Base.mul_prod),typeof(*)}, ::Base.IndexCartesian, A::AbstractSparseMatrixCSC{T}) where {F,T}
     nnzA = nnz(A)
     nzeros = widelength(A) - nnzA
     if nzeros == 0
@@ -2501,7 +2501,7 @@ function _mapreducecols!(f, op, R::AbstractArray, A::AbstractSparseMatrixCSC{Tv,
     R
 end
 
-function Base._mapreducedim!(f, op, R::AbstractArray, A::AbstractSparseMatrixCSC{T}) where T
+function Base._mapreducedim!(f::F, op::G, R::AbstractArray, A::AbstractSparseMatrixCSC{T}) where {F,G,T}
     require_one_based_indexing(A, R)
     lsiz = Base.check_reducedims(R,A)
     isempty(A) && return R
diff --git a/src/sparsevector.jl b/src/sparsevector.jl
index 375d66bc..d6f83fd6 100644
--- a/src/sparsevector.jl
+++ b/src/sparsevector.jl
@@ -324,7 +324,7 @@ julia> sparsevec([1, 3, 1, 2, 2], [true, true, false, false, false])
   [3]  =  1
 ```
 """
-function sparsevec(I::AbstractVector{<:Integer}, V::AbstractVector, combine::Function)
+function sparsevec(I::AbstractVector{<:Integer}, V::AbstractVector, combine::F) where {F<:Function}
     require_one_based_indexing(I, V)
     length(I) == length(V) ||
         throw(ArgumentError("index and value vectors must be the same length"))
@@ -338,7 +338,7 @@ function sparsevec(I::AbstractVector{<:Integer}, V::AbstractVector, combine::Fun
     _sparsevector!(Vector(I), Vector(V), len, combine)
 end
 
-function sparsevec(I::AbstractVector{<:Integer}, V::AbstractVector, len::Integer, combine::Function)
+function sparsevec(I::AbstractVector{<:Integer}, V::AbstractVector, len::Integer, combine::F) where {F<:Function}
     require_one_based_indexing(I, V)
     length(I) == length(V) ||
         throw(ArgumentError("index and value vectors must be the same length"))
@@ -363,10 +363,10 @@ sparsevec(I::AbstractVector, V::Union{Bool, AbstractVector{Bool}}) =
 sparsevec(I::AbstractVector, V::Union{Bool, AbstractVector{Bool}}, len::Integer) =
     sparsevec(I, V, len, |)
 
-sparsevec(I::AbstractVector, v::Number, combine::Function) =
+sparsevec(I::AbstractVector, v::Number, combine::F) where {F<:Function} =
     sparsevec(I, fill(v, length(I)), combine)
 
-sparsevec(I::AbstractVector, v::Number, len::Integer, combine::Function) =
+sparsevec(I::AbstractVector, v::Number, len::Integer, combine::F) where {F<:Function} =
     sparsevec(I, fill(v, length(I)), len, combine)
 
 
@@ -1669,7 +1669,7 @@ end
 Base.reducedim_initarray(A::SparseVectorUnion, region, v0, ::Type{R}) where {R} =
     fill!(Array{R}(undef, Base.to_shape(Base.reduced_indices(A, region))), v0)
 
-function Base._mapreduce(f, op, ::IndexCartesian, A::SparseVectorUnion)
+function Base._mapreduce(f::F, op::G, ::IndexCartesian, A::SparseVectorUnion) where {F,G}
     T = eltype(A)
     isempty(A) && return Base.mapreduce_empty(f, op, T)
     z = nnz(A)
@@ -1686,7 +1686,7 @@ Base._any(f, A::SparseVectorUnion, ::Colon) =
 Base._all(f, A::SparseVectorUnion, ::Colon) =
     iszero(length(A)) ? true  : Base._mapreduce(f, &, IndexCartesian(), A)
 
-function Base.mapreducedim!(f, op, R::AbstractVector, A::SparseVectorUnion)
+function Base.mapreducedim!(f::F, op::G, R::AbstractVector, A::SparseVectorUnion) where {F,G}
     # dim1 reduction could be safely replaced with a mapreduce
     if length(R) == 1
         I = firstindex(R)