diff --git a/src/PETSc.jl b/src/PETSc.jl
index d8782d40..0a463bb1 100644
--- a/src/PETSc.jl
+++ b/src/PETSc.jl
@@ -24,7 +24,7 @@ include("viewer.jl")
 include("options.jl")
 include("vec.jl")
 include("mat.jl")
-# include("matshell.jl")
+include("matshell.jl")
 # include("ksp.jl")
 # include("ref.jl")
 # include("pc.jl")
diff --git a/src/matshell.jl b/src/matshell.jl
index 98571bbd..53dd7cbd 100644
--- a/src/matshell.jl
+++ b/src/matshell.jl
@@ -1,60 +1,99 @@
 """
-    MatShell{T}(obj, m, n)
-
-Create a `m×n` PETSc shell matrix object wrapping `obj`.
-
-If `obj` is a `Function`, then the multiply action `obj(y,x)`; otherwise it calls `mul!(y, obj, x)`.
-This can be changed by defining `PETSc._mul!`.
-
+    MatShell(
+        petsclib::PetscLib,
+        obj::OType,
+        comm::MPI.Comm,
+        local_rows,
+        local_cols,
+        global_rows = LibPETSc.PETSC_DECIDE,
+        global_cols = LibPETSc.PETSC_DECIDE,
+    )
+
+Create a `global_rows X global_cols` PETSc shell matrix object wrapping `obj`
+with local size `local_rows X local_cols`.
+
+The `obj` will be registered as an `MATOP_MULT` function and if if `obj` is a
+`Function`, then the multiply action `obj(y,x)`; otherwise it calls `mul!(y,
+obj, x)`.
+
+# External Links
+$(_doc_external("Mat/MatCreateShell"))
+$(_doc_external("Mat/MatShellSetOperation"))
+$(_doc_external("Mat/MATOP_MULT"))
 """
-mutable struct MatShell{T,A} <: AbstractMat{T}
+mutable struct MatShell{PetscLib, PetscScalar, OType} <:
+               AbstractMat{PetscLib, PetscScalar}
     ptr::CMat
-    obj::A
+    obj::OType
 end
 
+struct MatOp{PetscLib, PetscInt, Op} end
+
+function (::MatOp{PetscLib, PetscInt, LibPETSc.MATOP_MULT})(
+    M::CMat,
+    cx::CVec,
+    cy::CVec,
+)::PetscInt where {PetscLib, PetscInt}
+    r_ctx = Ref{Ptr{Cvoid}}()
+    LibPETSc.MatShellGetContext(PetscLib, M, r_ctx)
+    ptr = r_ctx[]
+    mat = unsafe_pointer_to_objref(ptr)
 
-struct MatOp{T,Op} end
+    PetscScalar = getlib(PetscLib).PetscScalar
+    x = unsafe_localarray(VecPtr(PetscLib, cx); write = false)
+    y = unsafe_localarray(VecPtr(PetscLib, cy); read = false)
 
+    _mul!(y, mat, x)
 
-function _mul!(y,mat::MatShell{T,F},x) where {T, F<:Function}
+    Base.finalize(y)
+    Base.finalize(x)
+    return PetscInt(0)
+end
+
+function _mul!(
+    y,
+    mat::MatShell{PetscLib, PetscScalar, F},
+    x,
+) where {PetscLib, PetscScalar, F <: Function}
     mat.obj(y, x)
 end
 
-function _mul!(y,mat::MatShell{T},x) where {T}
+function _mul!(y, mat::MatShell, x) where {T}
     LinearAlgebra.mul!(y, mat.obj, x)
 end
 
-MatShell{T}(obj, m, n) where {T} = MatShell{T}(obj, MPI.COMM_SELF, m, n, m, n)
-
-
-@for_libpetsc begin
-    function MatShell{$PetscScalar}(obj::A, comm::MPI.Comm, m, n, M, N) where {A}
-        mat = MatShell{$PetscScalar,A}(C_NULL, obj)
-        # we use the MatShell object itsel
-        ctx = pointer_from_objref(mat)
-        @chk ccall((:MatCreateShell, $libpetsc), PetscErrorCode,
-          (MPI.MPI_Comm,$PetscInt,$PetscInt,$PetscInt,$PetscInt,Ptr{Cvoid},Ptr{CMat}),
-          comm, m, n, M, N, ctx, mat)
-
-        mulptr = @cfunction(MatOp{$PetscScalar, MATOP_MULT}(), $PetscInt, (CMat, CVec, CVec))
-        @chk ccall((:MatShellSetOperation, $libpetsc), PetscErrorCode, (CMat, MatOperation, Ptr{Cvoid}), mat, MATOP_MULT, mulptr)
-        return mat
-    end
-
-    function (::MatOp{$PetscScalar, MATOP_MULT})(M::CMat,cx::CVec,cy::CVec)::$PetscInt
-        r_ctx = Ref{Ptr{Cvoid}}()
-        @chk ccall((:MatShellGetContext, $libpetsc), PetscErrorCode, (CMat, Ptr{Ptr{Cvoid}}), M, r_ctx)
-        ptr = r_ctx[]
-        mat = unsafe_pointer_to_objref(ptr)
-
-        x = unsafe_localarray($PetscScalar, cx; write=false)
-        y = unsafe_localarray($PetscScalar, cy; read=false)
-
-        _mul!(y,mat,x)
-
-        Base.finalize(y)
-        Base.finalize(x)
-        return $PetscInt(0)
-    end
-
+# We have to use the macro here because of the @cfunction
+LibPETSc.@for_petsc function MatShell(
+    petsclib::$PetscLib,
+    obj::OType,
+    comm::MPI.Comm,
+    local_rows,
+    local_cols,
+    global_rows = LibPETSc.PETSC_DECIDE,
+    global_cols = LibPETSc.PETSC_DECIDE,
+) where {OType}
+    mat = MatShell{$PetscLib, $PetscScalar, OType}(C_NULL, obj)
+
+    # we use the MatShell object itself
+    ctx = pointer_from_objref(mat)
+
+    LibPETSc.MatCreateShell(
+        petsclib,
+        comm,
+        local_rows,
+        local_cols,
+        global_rows,
+        global_cols,
+        pointer_from_objref(mat),
+        mat,
+    )
+
+    mulptr = @cfunction(
+        MatOp{$PetscLib, $PetscInt, LibPETSc.MATOP_MULT}(),
+        $PetscInt,
+        (CMat, CVec, CVec)
+    )
+    LibPETSc.MatShellSetOperation(petsclib, mat, LibPETSc.MATOP_MULT, mulptr)
+
+    return mat
 end
diff --git a/src/vec.jl b/src/vec.jl
index 6f58df70..04780da0 100644
--- a/src/vec.jl
+++ b/src/vec.jl
@@ -18,6 +18,21 @@ Base.eltype(
 ) where {PetscLib, PetscScalar} = PetscScalar
 Base.size(v::AbstractVec) = (length(v),)
 
+"""
+    VecPtr(petsclib, v::Vector)
+
+Container type for a PETSc Vec that is passed from a function.
+"""
+mutable struct VecPtr{PetscLib, PetscScalar} <:
+               AbstractVec{PetscLib, PetscScalar}
+    ptr::CVec
+end
+function VecPtr(petsclib::PetscLib, ptr::CVec) where {PetscLib <: PetscLibType}
+    return VecPtr{PetscLib, petsclib.PetscScalar}(ptr)
+end
+VecPtr(::Type{PetscLib}, ptr::CVec) where {PetscLib <: PetscLibType} =
+    VecPtr(getlib(PetscLib), ptr)
+
 """
     VecSeq(petsclib, v::Vector)
 
diff --git a/test/matshell.jl b/test/matshell.jl
new file mode 100644
index 00000000..eb2c14ad
--- /dev/null
+++ b/test/matshell.jl
@@ -0,0 +1,22 @@
+using Test
+using PETSc
+using MPI
+
+@testset "MatShell" begin
+    for petsclib in PETSc.petsclibs
+        PETSc.initialize(petsclib)
+        PetscScalar = petsclib.PetscScalar
+
+        local_rows = 10
+        local_cols = 5
+        f!(x, y) = x .= [2y; 3y]
+        x_jl = collect
+
+        matshell =
+            PETSc.MatShell(petsclib, f!, MPI.COMM_SELF, local_rows, local_cols)
+        x = PetscScalar.(collect(1:5))
+        @test matshell * x == [2x; 3x]
+
+        PETSc.finalize(petsclib)
+    end
+end
diff --git a/test/runtests.jl b/test/runtests.jl
index a02d2207..28477ea8 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -2,3 +2,4 @@ include("init.jl")
 include("options.jl")
 include("vec.jl")
 include("mat.jl")
+include("matshell.jl")