diff --git a/include/LinearAlgebra/Matrix/coo_matrix.h b/include/LinearAlgebra/Matrix/coo_matrix.h
index d7ebd462..3eb8b60b 100644
--- a/include/LinearAlgebra/Matrix/coo_matrix.h
+++ b/include/LinearAlgebra/Matrix/coo_matrix.h
@@ -66,8 +66,8 @@ class SparseMatrixCOO
     int* column_indices_data() const;
     T* values_data() const;
 
-    template <typename U>
-    friend std::ostream& operator<<(std::ostream& stream, const SparseMatrixCOO<U>& matrix);
+    template <typename U, class MemorySpace2>
+    friend std::ostream& operator<<(std::ostream& stream, const SparseMatrixCOO<U, MemorySpace2>& matrix);
 
     void write_to_file(const std::string& filename) const;
 
@@ -81,18 +81,22 @@ class SparseMatrixCOO
     bool is_symmetric_ = false;
 };
 
-template <typename U>
-std::ostream& operator<<(std::ostream& stream, const SparseMatrixCOO<U>& matrix)
+template <typename U, class MemorySpace>
+std::ostream& operator<<(std::ostream& stream, const SparseMatrixCOO<U, MemorySpace>& matrix)
 {
     stream << "SparseMatrixCOO: " << matrix.rows_ << " x " << matrix.columns_ << "\n";
     stream << "Number of non-zeros (nnz): " << matrix.nnz_ << "\n";
     if (matrix.is_symmetric_) {
         stream << "Matrix is symmetric.\n";
     }
+    // Create host mirrors and deep_copy from device if necessary.
+    // If the View is already on host, deep_copy is a no-op.
+    auto h_values         = Kokkos::create_mirror_view_and_copy(Kokkos::HostSpace{}, matrix.values_);
+    auto h_column_indices = Kokkos::create_mirror_view_and_copy(Kokkos::HostSpace{}, matrix.column_indices_);
+    auto h_row_indices    = Kokkos::create_mirror_view_and_copy(Kokkos::HostSpace{}, matrix.row_indices_);
     stream << "Non-zero elements (row, column, value):\n";
     for (int i = 0; i < matrix.nnz_; ++i) {
-        stream << "(" << matrix.row_indices_(i) << ", " << matrix.column_indices_(i) << ", " << matrix.values_(i)
-               << ")\n";
+        stream << "(" << h_row_indices(i) << ", " << h_column_indices(i) << ", " << h_values(i) << ")\n";
     }
     return stream;
 }
diff --git a/include/LinearAlgebra/Matrix/csr_matrix.h b/include/LinearAlgebra/Matrix/csr_matrix.h
index 5f7afdae..2b2a8823 100644
--- a/include/LinearAlgebra/Matrix/csr_matrix.h
+++ b/include/LinearAlgebra/Matrix/csr_matrix.h
@@ -104,8 +104,8 @@ class SparseMatrixCSR
     KOKKOS_FUNCTION int* column_indices_data() const;
     KOKKOS_FUNCTION int* row_start_indices_data() const;
 
-    template <typename U>
-    friend std::ostream& operator<<(std::ostream& stream, const SparseMatrixCSR<U, MemorySpace>& matrix);
+    template <typename U, class MemorySpace2>
+    friend std::ostream& operator<<(std::ostream& stream, const SparseMatrixCSR<U, MemorySpace2>& matrix);
 
     template <class, class>
     friend class SparseMatrixCSR;