diff --git a/git-ref/src/lib.rs b/git-ref/src/lib.rs
index f202fc913b..9c26defa2e 100644
--- a/git-ref/src/lib.rs
+++ b/git-ref/src/lib.rs
@@ -28,6 +28,8 @@ pub mod mutable;
 ///
 pub mod name;
 ///
+pub mod namespace;
+///
 pub mod transaction;
 
 /// A validated and potentially partial reference name - it can safely be used for common operations.
diff --git a/git-ref/src/name.rs b/git-ref/src/name.rs
index 45588bd657..e859f43692 100644
--- a/git-ref/src/name.rs
+++ b/git-ref/src/name.rs
@@ -9,6 +9,7 @@ mod error {
 
     quick_error! {
         /// The error used in the [`PartialName`][super::PartialName]::try_from(…) implementations.
+        /// TODO: remove this error, turning it into the inner one. This is an unnecessary proxy
         #[derive(Debug)]
         #[allow(missing_docs)]
         pub enum Error {
diff --git a/git-ref/src/namespace.rs b/git-ref/src/namespace.rs
new file mode 100644
index 0000000000..63f30204c4
--- /dev/null
+++ b/git-ref/src/namespace.rs
@@ -0,0 +1,35 @@
+#![allow(missing_docs)]
+
+use crate::PartialName;
+use std::convert::TryInto;
+
+pub fn expand<'a, Name, E>(namespace: Name) -> Result<crate::mutable::FullName, expand::Error>
+where
+    Name: TryInto<PartialName<'a>, Error = E>,
+    expand::Error: From<E>,
+{
+    let _namespace = namespace.try_into()?;
+    todo!("impl")
+}
+
+pub mod expand {
+    use quick_error::quick_error;
+    use std::convert::Infallible;
+
+    quick_error! {
+        #[derive(Debug)]
+        pub enum Error {
+            RefnameValidation(err: crate::name::Error) {
+                display("The ref name or path is not a valid ref name")
+                from()
+                source(err)
+            }
+        }
+    }
+
+    impl From<Infallible> for Error {
+        fn from(_: Infallible) -> Self {
+            unreachable!("this impl is needed to allow passing a known valid partial path as parameter")
+        }
+    }
+}
diff --git a/git-ref/tests/namespace/mod.rs b/git-ref/tests/namespace/mod.rs
new file mode 100644
index 0000000000..50380446f9
--- /dev/null
+++ b/git-ref/tests/namespace/mod.rs
@@ -0,0 +1,28 @@
+mod expand {
+    #[test]
+    fn each_component_expands_to_the_namespace_prefix_individually() {
+        assert_eq!(
+            git_ref::namespace::expand("foo/bar").unwrap().as_bstr(),
+            "refs/namespaces/foo/refs/namespaces/bar/"
+        )
+    }
+
+    #[test]
+    #[ignore]
+    fn only_backslashes_are_valid_component_separators() {}
+
+    #[test]
+    #[ignore]
+    fn trailing_slashes_do_nothing() {}
+
+    #[test]
+    fn empty_namespaces_are_not_allowed() {
+        assert!(matches!(
+            git_ref::namespace::expand("").expect_err("empty invalid"),
+            git_ref::namespace::expand::Error::RefnameValidation(git_ref::name::Error::RefnameValidation {
+                err: git_validate::refname::Error::Tag(git_validate::tag::name::Error::Empty),
+                ..
+            })
+        ))
+    }
+}
diff --git a/git-ref/tests/refs-parallel.rs b/git-ref/tests/refs-parallel.rs
index ec9104928d..f6e7421a80 100644
--- a/git-ref/tests/refs-parallel.rs
+++ b/git-ref/tests/refs-parallel.rs
@@ -1,5 +1,6 @@
 type Result<T = ()> = std::result::Result<T, Box<dyn std::error::Error>>;
 
 mod file;
+mod namespace;
 mod packed;
 mod transaction;
diff --git a/git-ref/tests/refs.rs b/git-ref/tests/refs.rs
index ec9104928d..f6e7421a80 100644
--- a/git-ref/tests/refs.rs
+++ b/git-ref/tests/refs.rs
@@ -1,5 +1,6 @@
 type Result<T = ()> = std::result::Result<T, Box<dyn std::error::Error>>;
 
 mod file;
+mod namespace;
 mod packed;
 mod transaction;