diff --git a/src/macros.rs b/src/macros.rs
index 0149b1fd1846..5c5b8c2deac7 100644
--- a/src/macros.rs
+++ b/src/macros.rs
@@ -402,6 +402,21 @@ macro_rules! offset_of {
     }};
 }
 
+/// Defines constants with an accompanying doc comment pointing out their
+/// instability, and links to the crate documentation for usage guidelines.
+macro_rules! ct {
+    ($($it:item)+) => {
+$(
+/// This constant, among others often used in C for the purposes of denoting the
+/// latest value or limit in a set of constants, is likely to change upstream.
+/// For correct usage, see the [crate-level documentation][docs].
+///
+/// [docs]: index.html#usage-recommendations
+$it
+)+
+    };
+}
+
 #[cfg(test)]
 mod tests {
     use core::any::TypeId;
diff --git a/src/unix/linux_like/linux_l4re_shared.rs b/src/unix/linux_like/linux_l4re_shared.rs
index 041e2525d9bc..8cf206a6366f 100644
--- a/src/unix/linux_like/linux_l4re_shared.rs
+++ b/src/unix/linux_like/linux_l4re_shared.rs
@@ -690,7 +690,10 @@ pub const EI_CLASS: usize = 4;
 pub const ELFCLASSNONE: u8 = 0;
 pub const ELFCLASS32: u8 = 1;
 pub const ELFCLASS64: u8 = 2;
-pub const ELFCLASSNUM: usize = 3;
+
+ct! {
+    pub const ELFCLASSNUM: usize = 3;
+}
 
 pub const EI_DATA: usize = 5;
 pub const ELFDATANONE: u8 = 0;
@@ -821,7 +824,10 @@ pub const EM_ALPHA: u16 = 0x9026;
 // elf.h - Legal values for e_version (version).
 pub const EV_NONE: u32 = 0;
 pub const EV_CURRENT: u32 = 1;
-pub const EV_NUM: u32 = 2;
+
+ct! {
+    pub const EV_NUM: u32 = 2;
+}
 
 // elf.h - Legal values for p_type (segment type).
 pub const PT_NULL: u32 = 0;