diff --git a/components/servo_arc/lib.rs b/components/servo_arc/lib.rs
index aa79140e0440..c2e5dd65e223 100644
--- a/components/servo_arc/lib.rs
+++ b/components/servo_arc/lib.rs
@@ -182,7 +182,7 @@ impl<T> Arc<T> {
             // FIXME(emilio): Would be so amazing to have
             // std::intrinsics::type_name() around, so that we could also report
             // a real size.
-            NS_LogCtor(ptr as *const _, b"ServoArc\0".as_ptr() as *const _, 8);
+            NS_LogCtor(ptr as *mut _, b"ServoArc\0".as_ptr() as *const _, 8);
         }
 
         unsafe {
@@ -315,7 +315,7 @@ impl<T: ?Sized> Arc<T> {
         #[cfg(feature = "gecko_refcount_logging")]
         unsafe {
             NS_LogDtor(
-                self.ptr() as *const _,
+                self.ptr() as *mut _,
                 b"ServoArc\0".as_ptr() as *const _,
                 8,
             );
@@ -355,12 +355,12 @@ impl<T: ?Sized> Arc<T> {
 #[cfg(feature = "gecko_refcount_logging")]
 extern "C" {
     fn NS_LogCtor(
-        aPtr: *const std::os::raw::c_void,
+        aPtr: *mut std::os::raw::c_void,
         aTypeName: *const std::os::raw::c_char,
         aSize: u32,
     );
     fn NS_LogDtor(
-        aPtr: *const std::os::raw::c_void,
+        aPtr: *mut std::os::raw::c_void,
         aTypeName: *const std::os::raw::c_char,
         aSize: u32,
     );
@@ -762,7 +762,7 @@ impl<H, T> Arc<HeaderSlice<H, [T]>> {
             if !is_static {
                 // FIXME(emilio): Would be so amazing to have
                 // std::intrinsics::type_name() around.
-                NS_LogCtor(ptr as *const _, b"ServoArc\0".as_ptr() as *const _, 8)
+                NS_LogCtor(ptr as *mut _, b"ServoArc\0".as_ptr() as *const _, 8)
             }
         }
 
diff --git a/components/style/rule_tree/mod.rs b/components/style/rule_tree/mod.rs
index 8f255898fc87..c52b7874a70b 100644
--- a/components/style/rule_tree/mod.rs
+++ b/components/style/rule_tree/mod.rs
@@ -950,8 +950,8 @@ mod gecko_leak_checking {
     use std::os::raw::{c_char, c_void};
 
     extern "C" {
-        pub fn NS_LogCtor(aPtr: *const c_void, aTypeName: *const c_char, aSize: u32);
-        pub fn NS_LogDtor(aPtr: *const c_void, aTypeName: *const c_char, aSize: u32);
+        fn NS_LogCtor(aPtr: *mut c_void, aTypeName: *const c_char, aSize: u32);
+        fn NS_LogDtor(aPtr: *mut c_void, aTypeName: *const c_char, aSize: u32);
     }
 
     static NAME: &'static [u8] = b"RuleNode\0";
@@ -960,7 +960,7 @@ mod gecko_leak_checking {
     pub fn log_ctor(ptr: *const RuleNode) {
         let s = NAME as *const [u8] as *const u8 as *const c_char;
         unsafe {
-            NS_LogCtor(ptr as *const c_void, s, size_of::<RuleNode>() as u32);
+            NS_LogCtor(ptr as *mut c_void, s, size_of::<RuleNode>() as u32);
         }
     }
 
@@ -968,7 +968,7 @@ mod gecko_leak_checking {
     pub fn log_dtor(ptr: *const RuleNode) {
         let s = NAME as *const [u8] as *const u8 as *const c_char;
         unsafe {
-            NS_LogDtor(ptr as *const c_void, s, size_of::<RuleNode>() as u32);
+            NS_LogDtor(ptr as *mut c_void, s, size_of::<RuleNode>() as u32);
         }
     }