diff --git a/src/lib.rs b/src/lib.rs
index e0b097d8c0..018d903bd9 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -447,11 +447,11 @@ impl Fd {
         call::fdatasync(self.raw())
     }
     #[inline]
-    pub fn ftruncate(self, len: usize) -> Result<()> {
+    pub fn ftruncate(&self, len: usize) -> Result<()> {
         call::ftruncate(self.raw(), len)
     }
     #[inline]
-    pub fn futimens(self, times: &[data::TimeSpec; 2]) -> Result<()> {
+    pub fn futimens(&self, times: &[data::TimeSpec; 2]) -> Result<()> {
         call::futimens(self.raw(), times)
     }
     /* TODO: Support unlinkat using std_fs_call