diff --git a/devices/src/register_space/register.rs b/devices/src/register_space/register.rs
index 3b113f9537..44beaf5e61 100644
--- a/devices/src/register_space/register.rs
+++ b/devices/src/register_space/register.rs
@@ -6,7 +6,8 @@ use std;
 use std::boxed::Box;
 use std::cmp::{max, min, Ord, Ordering, PartialEq, PartialOrd};
 use std::mem::size_of;
-use std::sync::{Arc, Mutex, MutexGuard};
+use std::sync::{Arc, MutexGuard};
+use sync::Mutex;
 
 use data_model::DataInit;
 
@@ -216,7 +217,7 @@ impl<T: RegisterValue> Register<T> {
     }
 
     fn lock(&self) -> MutexGuard<RegisterInner<T>> {
-        self.inner.lock().expect("fail to lock register")
+        self.inner.lock()
     }
 }
 
@@ -562,16 +563,16 @@ mod tests {
 
         let s2 = state.clone();
         r.set_write_cb(move |val: u8| {
-            *s2.lock().unwrap() = val as u8;
+            *s2.lock() = val as u8;
             val
         });
         let data: [u8; 4] = [0, 0, 0, 0xff];
         r.write_bar(0, &data);
-        assert_eq!(*state.lock().unwrap(), 0xf);
+        assert_eq!(*state.lock(), 0xf);
         r.set_value(0xab);
-        assert_eq!(*state.lock().unwrap(), 0xf);
+        assert_eq!(*state.lock(), 0xf);
         let data: [u8; 1] = [0xfc];
         r.write_bar(3, &data);
-        assert_eq!(*state.lock().unwrap(), 0xc);
+        assert_eq!(*state.lock(), 0xc);
     }
 }
diff --git a/devices/src/register_space/register_space.rs b/devices/src/register_space/register_space.rs
index a8e856b708..8b3c1e87c5 100644
--- a/devices/src/register_space/register_space.rs
+++ b/devices/src/register_space/register_space.rs
@@ -95,7 +95,8 @@ impl MMIOSpace {
 mod tests {
     use super::super::{RegisterSpec, StaticRegister, StaticRegisterSpec};
     use super::*;
-    use std::sync::{Arc, Mutex};
+    use std::sync::Arc;
+    use sync::Mutex;
 
     #[test]
     fn mmio_no_reg() {
@@ -216,7 +217,7 @@ mod tests {
         mmio.add_register(reg.clone());
         let state_clone = state.clone();
         reg.set_write_cb(move |val: u32| {
-            *state_clone.lock().unwrap() = val;
+            *state_clone.lock() = val;
             val
         });
 
@@ -224,7 +225,7 @@ mod tests {
         mmio.read_bar(0, &mut data);
         assert_eq!([8, 7, 0xdd, 0xcc, 0xbb, 0xaa, 2, 1], data);
         mmio.write_bar(0, &[0, 0, 0, 0, 0, 0, 0, 0]);
-        assert_eq!(0xaa0bccd0, *state.lock().unwrap());
+        assert_eq!(0xaa0bccd0, *state.lock());
     }
 
     #[test]