diff --git a/core-foundation-sys/Cargo.toml b/core-foundation-sys/Cargo.toml
index 769fbc4..f1dd3e3 100644
--- a/core-foundation-sys/Cargo.toml
+++ b/core-foundation-sys/Cargo.toml
@@ -3,7 +3,7 @@ name = "core-foundation-sys"
 description = "Bindings to Core Foundation for OS X"
 homepage = "https://github.com/servo/core-foundation-rs"
 repository = "https://github.com/servo/core-foundation-rs"
-version = "0.4.1"
+version = "0.4.2"
 authors = ["The Servo Project Developers"]
 license = "MIT / Apache-2.0"
 build = "build.rs"
diff --git a/core-foundation-sys/src/number.rs b/core-foundation-sys/src/number.rs
index 05758f3..3a5c09f 100644
--- a/core-foundation-sys/src/number.rs
+++ b/core-foundation-sys/src/number.rs
@@ -37,8 +37,9 @@ pub static kCFNumberFloat64Type:   CFNumberType = 6;
 // static kCFNumberCGFloatType:   CFNumberType = 16;
 // static kCFNumberMaxType:       CFNumberType = 16;
 
-#[repr(C)]
-pub struct __CFNumber;
+// This is an enum due to zero-sized types warnings.
+// For more details see https://github.com/rust-lang/rust/issues/27303
+pub enum __CFNumber {}
 
 pub type CFNumberRef = *const __CFNumber;
 
diff --git a/core-foundation/Cargo.toml b/core-foundation/Cargo.toml
index dd3775b..e338b16 100644
--- a/core-foundation/Cargo.toml
+++ b/core-foundation/Cargo.toml
@@ -3,13 +3,13 @@ name = "core-foundation"
 description = "Bindings to Core Foundation for OS X"
 homepage = "https://github.com/servo/core-foundation-rs"
 repository = "https://github.com/servo/core-foundation-rs"
-version = "0.4.1"
+version = "0.4.2"
 authors = ["The Servo Project Developers"]
 license = "MIT / Apache-2.0"
 
 [dependencies.core-foundation-sys]
 path = "../core-foundation-sys"
-version = "0.4.0"
+version = "0.4.2"
 
 [dependencies]
 libc = "0.2"
diff --git a/core-foundation/src/runloop.rs b/core-foundation/src/runloop.rs
index 5655535..ccc1f78 100644
--- a/core-foundation/src/runloop.rs
+++ b/core-foundation/src/runloop.rs
@@ -125,8 +125,9 @@ mod test {
 
 
         let run_loop_timer = CFRunLoopTimer::new(now + 0.20f64, 0f64, 0, 0, timer_popped, &mut context);
-        run_loop.add_timer(&run_loop_timer, kCFRunLoopDefaultMode);
-
+        unsafe {
+            run_loop.add_timer(&run_loop_timer, kCFRunLoopDefaultMode);
+        }
         CFRunLoop::run_current();
     }