diff --git a/const-oid/src/lib.rs b/const-oid/src/lib.rs
index 5ad5dd666..1a86e2167 100644
--- a/const-oid/src/lib.rs
+++ b/const-oid/src/lib.rs
@@ -181,6 +181,26 @@ impl ObjectIdentifier {
             Err(err) => Err(err),
         }
     }
+
+    /// Does this OID start with the other OID?
+    pub fn starts_with(&self, other: ObjectIdentifier) -> bool {
+        let mut self_arcs = self.arcs();
+
+        for other_arc in other.arcs() {
+            match self_arcs.next() {
+                Some(arc) => {
+                    if arc != other_arc {
+                        return false;
+                    }
+                }
+                None => {
+                    return false;
+                }
+            }
+        }
+
+        true
+    }
 }
 
 impl<'a> ObjectIdentifier<&'a [u8]> {
diff --git a/const-oid/tests/lib.rs b/const-oid/tests/lib.rs
index e91dfc6ca..7efb0f060 100644
--- a/const-oid/tests/lib.rs
+++ b/const-oid/tests/lib.rs
@@ -28,6 +28,11 @@ const EXAMPLE_OID_LARGE_ARC_BER: &[u8] = &hex!("0992268993F22C640101");
 const EXAMPLE_OID_LARGE_ARC: ObjectIdentifier =
     ObjectIdentifier::new_unwrap("0.9.2342.19200300.100.1.1");
 
+/// Create an OID from a string.
+pub fn oid(s: &str) -> ObjectIdentifier {
+    ObjectIdentifier::new(s).unwrap()
+}
+
 #[test]
 fn from_bytes() {
     let oid0 = ObjectIdentifier::from_bytes(EXAMPLE_OID_0_BER).unwrap();
@@ -193,17 +198,26 @@ fn parse_invalid_second_arc() {
 
 #[test]
 fn parent() {
-    let oid = ObjectIdentifier::new("1.2.3.4").unwrap();
-    let parent = oid.parent().unwrap();
-    assert_eq!(parent, ObjectIdentifier::new("1.2.3").unwrap());
+    let child = oid("1.2.3.4");
+    let parent = child.parent().unwrap();
+    assert_eq!(parent, oid("1.2.3"));
     assert_eq!(parent.parent(), None);
 }
 
 #[test]
 fn push_arc() {
-    let oid = ObjectIdentifier::new("1.2.3").unwrap();
-    assert_eq!(
-        oid.push_arc(4).unwrap(),
-        ObjectIdentifier::new("1.2.3.4").unwrap()
-    );
+    let parent = oid("1.2.3");
+    assert_eq!(parent.push_arc(4).unwrap(), oid("1.2.3.4"));
+}
+
+#[test]
+fn starts_with() {
+    let child = ObjectIdentifier::new("1.2.3.4.5").unwrap();
+    assert!(child.starts_with(oid("1.2.3.4.5")));
+    assert!(child.starts_with(oid("1.2.3.4")));
+    assert!(child.starts_with(oid("1.2.3")));
+
+    assert!(!child.starts_with(oid("1.2.4")));
+    assert!(!child.starts_with(oid("2.2.3")));
+    assert!(!child.starts_with(oid("1.2.3.4.5.6")));
 }