diff --git a/src/libcore/ptr.rs b/src/libcore/ptr.rs
index 780638f98b7..8718ad2274b 100644
--- a/src/libcore/ptr.rs
+++ b/src/libcore/ptr.rs
@@ -68,10 +68,10 @@ unsafe fn position<T>(buf: *T, f: fn(T) -> bool) -> uint {
 #[inline(always)]
 pure fn null<T>() -> *T unsafe { ret unsafe::reinterpret_cast(0u); }
 
-#[doc = "Returns true if the pointer is equal to the null pointer"]
+#[doc = "Returns true if the pointer is equal to the null pointer."]
 pure fn is_null<T>(ptr: *const T) -> bool { ptr == null() }
 
-#[doc = "Returns true if the pointer is not equal to the null pointer"]
+#[doc = "Returns true if the pointer is not equal to the null pointer."]
 pure fn is_not_null<T>(ptr: *const T) -> bool { !is_null(ptr) }
 
 #[doc = "