diff --git a/base/fs.jl b/base/fs.jl
index c44dd47272d3a7..1e9cb80b9734dc 100644
--- a/base/fs.jl
+++ b/base/fs.jl
@@ -171,7 +171,7 @@ function write(f::File, buf::Ptr{UInt8}, len::Integer, offset::Integer=-1)
     if !f.open
         error("file is not open")
     end
-    err = ccall(:jl_fs_write, Int32, (Int32, Ptr{UInt8}, Csize_t, Csize_t),
+    err = ccall(:jl_fs_write, Int32, (Int32, Ptr{UInt8}, Csize_t, Int64),
                 f.handle, buf, len, offset)
     uv_error("write",err)
     len
diff --git a/src/jl_uv.c b/src/jl_uv.c
index 9d9c94dfb96a28..37615cbd156c8c 100644
--- a/src/jl_uv.c
+++ b/src/jl_uv.c
@@ -452,7 +452,7 @@ DLLEXPORT int jl_fs_chmod(char *path, int mode)
     return ret;
 }
 
-DLLEXPORT int jl_fs_write(int handle, char *data, size_t len, size_t offset)
+DLLEXPORT int jl_fs_write(int handle, char *data, size_t len, int64_t offset)
 {
     uv_fs_t req;
     uv_buf_t buf[1];