diff --git a/build.rs b/build.rs
index 0de38e02ea..e320c82815 100644
--- a/build.rs
+++ b/build.rs
@@ -55,7 +55,6 @@ fn main() {
 
     // Priorities
     for i in 0..(1 << bits) + 1 {
-        let c = Ident::new(format!("C{}", i));
         let p = Ident::new(format!("P{}", i));
         let u = Ident::new(format!("U{}", i));
 
@@ -76,15 +75,6 @@ fn main() {
             quote! {
                 #[doc = #doc]
                 pub type #p = P<::typenum::#u>;
-
-                impl #p {
-                    /// Turns this priority into a ceiling
-                    pub fn as_ceiling(&self) -> &#c {
-                        unsafe {
-                            ::core::mem::transmute(self)
-                        }
-                    }
-                }
             },
         );
     }
diff --git a/src/lib.rs b/src/lib.rs
index 239c80234c..3d08402d30 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -436,7 +436,7 @@ extern crate typenum;
 
 use core::cell::UnsafeCell;
 use core::marker::PhantomData;
-use core::ptr;
+use core::{mem, ptr};
 
 use cortex_m::ctxt::Context;
 use cortex_m::interrupt::Nr;
@@ -719,6 +719,15 @@ pub struct P<T> {
     _marker: PhantomData<T>,
 }
 
+impl<N> P<N> {
+    /// Turns this priority into a ceiling
+    pub fn as_ceiling(&self) -> &C<N> {
+        unsafe {
+            mem::transmute(self)
+        }
+    }
+}
+
 impl<T> P<T>
 where
     T: Unsigned,