diff --git a/posix/fd.cpp b/posix/fd.cpp
index dc04de17..c910d8b1 100644
--- a/posix/fd.cpp
+++ b/posix/fd.cpp
@@ -180,14 +180,26 @@ fd::pwrite (const void *buf, size_t count, size_t offset)
         ::pwrite (native (), buf, count, offset)
     );
 #else
-    DWORD written;
-    OVERLAPPED overlapped;
-    memset (&overlapped, 0, sizeof (overlapped));
-    overlapped.Offset = offset & 0xffffffff;
-    overlapped.OffsetHigh = offset >> 32u;
+    // Ideally we'd to use something like WriteFile with an OVERLAPPED
+    // structure applied to the handle extracted with _get_osfhandle (m_fd).
+    //
+    // But this modifies the file cursor, and if we need to seek anyway then
+    // we may as well just emulate the entire with a query and two seeks.
+    //
+    // NOTE: It is thus possible to observe the fd with an 'incorrect' file
+    // pointer. Do not rely on POSIX behaviour across multiple threads.
 
-    if (!WriteFile (reinterpret_cast<HANDLE> (_get_osfhandle (m_fd)), buf, count, &written, &overlapped))
-        error::throw_code (EINVAL);
+    auto const initial = lseek (0, SEEK_CUR);
+    ssize_t written = -1;
+    try {
+        (void)lseek (offset, SEEK_SET);
+        written = write (buf, count);
+    } catch (...) {
+        (void)lseek (initial, SEEK_SET);
+        throw;
+    }
+
+    (void)lseek (initial, SEEK_SET);
     return written;
 #endif
 }