diff --git a/ffi.rs b/ffi.rs
index 20c8137..b0b192e 100644
--- a/ffi.rs
+++ b/ffi.rs
@@ -27,7 +27,7 @@ pub static COLOR_TYPE_RGBA: c_int = 6;
 pub type png_struct = c_void;
 pub type png_info = c_void;
 
-pub extern {
+extern {
     // libc routines needed
     pub fn setjmp(env: *c_void) -> c_int;
 
@@ -65,4 +65,4 @@ pub extern {
     pub fn png_set_IHDR(png_ptr: *png_struct, info_ptr: *mut png_info, width: u32, height: u32, bit_depth: c_int, color_type: c_int, interlace_method: c_int, compression_method: c_int, filter_method: c_int);
     pub fn png_set_pHYs(png_ptr: *png_struct, info_ptr: *mut png_info, res_x: u32, res_y: u32, unit_type: c_int);
     pub fn png_set_rows(png_ptr: *png_struct, info_ptr: *mut png_info, row_pointers: **u8);
-}
\ No newline at end of file
+}
diff --git a/lib.rs b/lib.rs
index c8f7938..b3de270 100644
--- a/lib.rs
+++ b/lib.rs
@@ -94,10 +94,10 @@ pub fn load_png(path: &Path) -> Result<Image,~str> {
             _ => fail!(~"color type not supported"),
         };
 
-        let mut image_data = vec::from_elem(width * height * pixel_width as uint, 0u8);
+        let mut image_data = vec::from_elem((width * height * pixel_width) as uint, 0u8);
         let image_buf = vec::raw::to_mut_ptr(image_data);
         let row_pointers: ~[*mut u8] = do vec::from_fn(height as uint) |idx| {
-            ptr::mut_offset(image_buf, (width * pixel_width as uint) * idx)
+            ptr::mut_offset(image_buf, (((width * pixel_width) as uint) * idx) as int)
         };
 
         ffi::png_read_image(png_ptr, vec::raw::to_ptr(row_pointers));
@@ -178,7 +178,7 @@ pub fn store_png(img: &Image, path: &Path) -> Result<(),~str> {
 
         let image_buf = vec::raw::to_ptr(img.pixels);
         let row_pointers: ~[*u8] = do vec::from_fn(img.height as uint) |idx| {
-            ptr::offset(image_buf, (img.width * pixel_width as uint) * idx)
+            ptr::offset(image_buf, (((img.width * pixel_width) as uint) * idx) as int)
         };
         ffi::png_set_rows(&*png_ptr, info_ptr, vec::raw::to_ptr(row_pointers));