diff --git a/Source/Operations/source/Copying/CopyingJob.cpp b/Source/Operations/source/Copying/CopyingJob.cpp
index 4191fec94..51f8634a6 100644
--- a/Source/Operations/source/Copying/CopyingJob.cpp
+++ b/Source/Operations/source/Copying/CopyingJob.cpp
@@ -929,9 +929,9 @@ CopyingJob::StepResult CopyingJob::CopyNativeFileToNativeFile(vfs::NativeHost &_
     }
 
     auto read_buffer = m_Buffers[0].get(), write_buffer = m_Buffers[1].get();
-    const uint32_t src_preffered_io_size =
+    const uint32_t src_preferred_io_size =
         src_fs_info.basic.io_size < m_BufferSize ? src_fs_info.basic.io_size : m_BufferSize;
-    const uint32_t dst_preffered_io_size =
+    const uint32_t dst_preferred_io_size =
         dst_fs_info.basic.io_size < m_BufferSize ? dst_fs_info.basic.io_size : m_BufferSize;
     constexpr int max_io_loops = 5; // looked in Apple's copyfile() - treat 5 zero-resulting reads/writes as an error
     uint32_t bytes_to_write = 0;
@@ -951,7 +951,7 @@ CopyingJob::StepResult CopyingJob::CopyNativeFileToNativeFile(vfs::NativeHost &_
                        bytes_to_write,
                        destination_fd,
                        write_buffer,
-                       dst_preffered_io_size,
+                       dst_preferred_io_size,
                        &destination_bytes_written,
                        &write_return,
                        &_dst_path,
@@ -961,7 +961,7 @@ CopyingJob::StepResult CopyingJob::CopyNativeFileToNativeFile(vfs::NativeHost &_
             int write_loops = 0;
             while( left_to_write > 0 ) {
                 int64_t n_written =
-                    write(destination_fd, write_buffer + has_written, std::min(left_to_write, dst_preffered_io_size));
+                    write(destination_fd, write_buffer + has_written, std::min(left_to_write, dst_preferred_io_size));
                 if( n_written > 0 ) {
                     has_written += n_written;
                     left_to_write -= n_written;
@@ -984,14 +984,15 @@ CopyingJob::StepResult CopyingJob::CopyNativeFileToNativeFile(vfs::NativeHost &_
 
         // <<<--- reading in current thread --->>>
         // here we handle the case in which source io size is much smaller than dest's io size
-        uint32_t to_read = std::max(src_preffered_io_size, dst_preffered_io_size);
+        uint32_t to_read = std::max(src_preferred_io_size, dst_preferred_io_size);
         if( src_stat_buffer.st_size - source_bytes_read < to_read )
             to_read = uint32_t(src_stat_buffer.st_size - source_bytes_read);
         uint32_t has_read = 0;                 // amount of bytes read into buffer this time
         int read_loops = 0;                    // amount of zero-resulting reads
         std::optional<StepResult> read_return; // optional storage for error returning
         while( to_read != 0 ) {
-            int64_t read_result = read(source_fd, read_buffer + has_read, src_preffered_io_size);
+            const int64_t read_result = read(source_fd, read_buffer + has_read, to_read);
+            assert(read_result <= static_cast<int64_t>(to_read));
             if( read_result > 0 ) {
                 if( _source_data_feedback )
                     _source_data_feedback(read_buffer + has_read, static_cast<unsigned>(read_result));
diff --git a/Source/Operations/tests/Copying_IT.mm b/Source/Operations/tests/Copying_IT.mm
index 4c2b954ae..511a7ebff 100644
--- a/Source/Operations/tests/Copying_IT.mm
+++ b/Source/Operations/tests/Copying_IT.mm
@@ -14,6 +14,7 @@
 #include <span>
 #include <fstream>
 #include <compare>
+#include <thread>
 
 using nc::ops::Copying;
 using nc::ops::CopyingOptions;
@@ -1374,6 +1375,40 @@ Copying op(FetchItems("/System/Library/Kernels/", {"kernel"}, *TestEnv().vfs_nat
     VFSEasyDelete(target_dir.c_str(), host);
 }
 
+TEST_CASE(PREFIX "Copying a native file that is being written to")
+{
+    TempTestDir dir;
+    const std::filesystem::path p = dir.directory / "a";
+    static constexpr size_t max_size = 100'000'000;
+    
+    std::atomic_bool stop = false;
+    std::thread t([p, &stop] {
+        const int f = open(p.c_str(), O_WRONLY | O_CREAT, S_IWUSR | S_IRUSR);
+        REQUIRE(f >= 0);
+        for(size_t i = 0; stop == false && i < max_size; ++i ) {
+            write(f, &f, 1);
+        }
+        close(f);
+    });
+
+    CopyingOptions opts;
+    opts.docopy = true;
+    auto host = TestEnv().vfs_native;
+    Copying op(FetchItems(dir.directory, {"a"}, *host), dir.directory / "b", host, opts);
+    op.Start();
+    op.Wait();
+
+    stop = true;
+    t.join();
+
+    REQUIRE(op.State() == OperationState::Completed);
+    REQUIRE(std::filesystem::status(dir.directory / "b").type() == std::filesystem::file_type::regular);
+    const size_t sz_a = std::filesystem::file_size(p);
+    const size_t sz_b = std::filesystem::file_size(dir.directory / "b");
+    CHECK(sz_a < max_size);
+    CHECK(sz_b < sz_a);
+}
+
 static std::vector<std::byte> MakeNoise(size_t _size)
 {
     std::vector<std::byte> bytes(_size);