diff --git a/include/uv.h b/include/uv.h
index 18fdb3198..5c993b451 100644
--- a/include/uv.h
+++ b/include/uv.h
@@ -1632,7 +1632,7 @@ UV_EXTERN int uv_fs_unlink(uv_loop_t* loop, uv_fs_t* req, const char* path,
     uv_fs_cb cb);
 
 UV_EXTERN int uv_fs_write(uv_loop_t* loop, uv_fs_t* req, uv_file file,
-    void* buf, size_t length, int64_t offset, uv_fs_cb cb);
+    const void* buf, size_t length, int64_t offset, uv_fs_cb cb);
 
 UV_EXTERN int uv_fs_mkdir(uv_loop_t* loop, uv_fs_t* req, const char* path,
     int mode, uv_fs_cb cb);
diff --git a/src/unix/fs.c b/src/unix/fs.c
index 75b234376..142e4a0b3 100644
--- a/src/unix/fs.c
+++ b/src/unix/fs.c
@@ -934,13 +934,13 @@ int uv_fs_utime(uv_loop_t* loop,
 int uv_fs_write(uv_loop_t* loop,
                 uv_fs_t* req,
                 uv_file file,
-                void* buf,
+                const void* buf,
                 size_t len,
                 int64_t off,
                 uv_fs_cb cb) {
   INIT(WRITE);
   req->file = file;
-  req->buf = buf;
+  req->buf = (void*) buf;
   req->len = len;
   req->off = off;
   POST;
diff --git a/src/win/fs.c b/src/win/fs.c
index 2ea2cb1c6..9d4d7ff84 100644
--- a/src/win/fs.c
+++ b/src/win/fs.c
@@ -1521,12 +1521,12 @@ int uv_fs_read(uv_loop_t* loop, uv_fs_t* req, uv_file fd, void* buf,
 }
 
 
-int uv_fs_write(uv_loop_t* loop, uv_fs_t* req, uv_file fd, void* buf,
+int uv_fs_write(uv_loop_t* loop, uv_fs_t* req, uv_file fd, const void* buf,
     size_t length, int64_t offset, uv_fs_cb cb) {
   uv_fs_req_init(loop, req, UV_FS_WRITE, cb);
 
   req->fd = fd;
-  req->buf = buf;
+  req->buf = (void*) buf;
   req->length = length;
   req->offset = offset;