diff --git a/src/libstd/sys/unix/os.rs b/src/libstd/sys/unix/os.rs
index 15f04d37674..e99e2c50d1d 100644
--- a/src/libstd/sys/unix/os.rs
+++ b/src/libstd/sys/unix/os.rs
@@ -141,7 +141,8 @@ pub fn split_paths(unparsed: &OsStr) -> SplitPaths {
     fn is_colon(b: &u8) -> bool { *b == b':' }
     let unparsed = unparsed.as_bytes();
     SplitPaths {
-        iter: unparsed.split(is_colon).map(bytes_to_path)
+        iter: unparsed.split(is_colon as fn(&u8) -> bool)
+                      .map(bytes_to_path as fn(&'a [u8]) -> PathBuf)
     }
 }