diff --git a/src/librustpkg/util.rs b/src/librustpkg/util.rs
index dddf494856e9..60367fd9aa64 100644
--- a/src/librustpkg/util.rs
+++ b/src/librustpkg/util.rs
@@ -380,7 +380,7 @@ pub fn link_exe(_src: &Path, _dest: &Path) -> bool {
 #[cfg(target_os = "freebsd")]
 #[cfg(target_os = "macos")]
 pub fn link_exe(src: &Path, dest: &Path) -> bool {
-    use std::{libc, str};
+    use std::libc;
     unsafe {
         do src.to_str().as_c_str |src_buf| {
             do dest.to_str().as_c_str |dest_buf| {
diff --git a/src/libstd/run.rs b/src/libstd/run.rs
index d8fc68d64225..b6cc556af106 100644
--- a/src/libstd/run.rs
+++ b/src/libstd/run.rs
@@ -23,7 +23,6 @@ use option::{Some, None};
 use os;
 use prelude::*;
 use ptr;
-use str;
 use task;
 use vec::ImmutableVector;
 
diff --git a/src/libstd/str.rs b/src/libstd/str.rs
index ab3d362ba792..5bd084b8796e 100644
--- a/src/libstd/str.rs
+++ b/src/libstd/str.rs
@@ -3116,6 +3116,28 @@ mod tests {
         }
     }
 
+    #[test]
+    fn test_as_c_str() {
+        let a = ~"";
+        do a.as_c_str |buf| {
+            unsafe {
+                assert_eq!(*ptr::offset(buf, 0), 0);
+            }
+        }
+
+        let a = ~"hello";
+        do a.as_c_str |buf| {
+            unsafe {
+                assert_eq!(*ptr::offset(buf, 0), 'h' as libc::c_char);
+                assert_eq!(*ptr::offset(buf, 1), 'e' as libc::c_char);
+                assert_eq!(*ptr::offset(buf, 2), 'l' as libc::c_char);
+                assert_eq!(*ptr::offset(buf, 3), 'l' as libc::c_char);
+                assert_eq!(*ptr::offset(buf, 4), 'o' as libc::c_char);
+                assert_eq!(*ptr::offset(buf, 5), 0);
+            }
+        }
+    }
+
     #[test]
     fn test_subslice_offset() {
         let a = "kernelsprite";