diff --git a/crates/radicle-oid/src/lib.rs b/crates/radicle-oid/src/lib.rs
index 3568ffa5..1c2bc90a 100644
--- a/crates/radicle-oid/src/lib.rs
+++ b/crates/radicle-oid/src/lib.rs
@@ -87,6 +87,11 @@ pub enum Oid {
 // for forwards compatibility: What if another hash with digests of the same
 // length becomes popular?
 impl Oid {
+    /// A SHA-1 object identifier with all digest bytes set to zero.
+    /// This is sometimes used as a sentinel value to indicate the absence of
+    /// an object.
+    /// To compare whether an object identifier is zero, prefer the method
+    /// [`Oid::is_zero`] over checking equality with this constant.
     pub const ZERO_SHA1: Self = Self::Sha1([0u8; SHA1_DIGEST_LEN]);
 
     pub fn from_sha1(digest: [u8; SHA1_DIGEST_LEN]) -> Self {
diff --git a/crates/radicle/src/storage/refs.rs b/crates/radicle/src/storage/refs.rs
index 08d69ce8..639dd5f9 100644
--- a/crates/radicle/src/storage/refs.rs
+++ b/crates/radicle/src/storage/refs.rs
@@ -177,7 +177,7 @@ impl Refs {
         let mut buf = String::new();
 
         for (name, oid) in self.0.iter() {
-            debug_assert_ne!(oid, &Oid::ZERO_SHA1);
+            debug_assert!(!oid.is_zero());
             debug_assert_ne!(name, &SIGREFS_BRANCH.to_ref_string());
 
             buf.push_str(&oid.to_string());