diff --git a/crates/aaf/src/aaf/read.rs b/crates/aaf/src/aaf/read.rs
index 206c2ead3..753675ce1 100644
--- a/crates/aaf/src/aaf/read.rs
+++ b/crates/aaf/src/aaf/read.rs
@@ -172,6 +172,7 @@ impl R<'_> {
         let mut sample_rate = tag("FilmCraft Audio Sample Rate").and_then(|s| s.parse().ok()).unwrap_or(0u32);
         let mut comp = Composition {
             name,
+            aaf_mob_id: c.mob_id(pid::MOB_ID).map(|id| hex(&id)),
             rate,
             sample_rate: 48_000,
             width: 1920,
diff --git a/crates/aaf/src/aaf/tests.rs b/crates/aaf/src/aaf/tests.rs
index 2773fda6d..ca2196d3f 100644
--- a/crates/aaf/src/aaf/tests.rs
+++ b/crates/aaf/src/aaf/tests.rs
@@ -125,7 +125,14 @@ fn edits_tagged_with_either_usage_code_both_import() {
     old.set(pid::USAGE_CODE, Value::Data(def::USAGE_TOP_LEVEL_OLD.to_vec()));
     mobs.push(old);
     let mixed = store::write(&root, craft_cfb::Version::V4).unwrap();
-    let mut names: Vec<String> = read_clean(&mixed).compositions.into_iter().map(|c| c.name).collect();
+    let document = read_clean(&mixed);
+    let mut ids: Vec<_> = document.compositions.iter().map(|c| c.aaf_mob_id.as_deref().unwrap()).collect();
+    assert_eq!(ids.len(), 2);
+    assert!(ids.iter().all(|id| id.len() == 64 && id.bytes().all(|b| b.is_ascii_hexdigit() && !b.is_ascii_uppercase())));
+    ids.sort_unstable();
+    ids.dedup();
+    assert_eq!(ids.len(), 2, "each composition keeps its own MobID");
+    let mut names: Vec<String> = document.compositions.into_iter().map(|c| c.name).collect();
     names.sort();
     assert_eq!(names, ["Old", "S"]);
 }
diff --git a/crates/aaf/src/model.rs b/crates/aaf/src/model.rs
index 3dff507be..e6bc79140 100644
--- a/crates/aaf/src/model.rs
+++ b/crates/aaf/src/model.rs
@@ -32,6 +32,10 @@ pub struct Document {
 #[derive(Clone, Debug, PartialEq)]
 pub struct Composition {
     pub name: String,
+    /// AAF CompositionMob identifier as 64 lowercase hexadecimal digits. OMF has no equivalent.
+    /// It is a read identity for applications that let a user choose among compositions; writers
+    /// generate fresh format identifiers and do not preserve it.
+    pub aaf_mob_id: Option<String>,
     pub rate: FrameRate,
     pub sample_rate: u32,
     pub width: u32,
diff --git a/crates/aaf/src/omf/read.rs b/crates/aaf/src/omf/read.rs
index 50e4b270c..d45b6ff63 100644
--- a/crates/aaf/src/omf/read.rs
+++ b/crates/aaf/src/omf/read.rs
@@ -153,6 +153,7 @@ impl R<'_, '_> {
         let name = self.string(m, "OMFI:MOBJ:Name").unwrap_or_else(|| "Sequence".into());
         let mut comp = Composition {
             name,
+            aaf_mob_id: None,
             rate: FrameRate::FPS_25,
             sample_rate: 48_000,
             width: 1920,
diff --git a/crates/aaf/src/testdoc.rs b/crates/aaf/src/testdoc.rs
index 81db0a158..c2740e1e7 100644
--- a/crates/aaf/src/testdoc.rs
+++ b/crates/aaf/src/testdoc.rs
@@ -52,7 +52,18 @@ pub(crate) fn two_clips(rate: FrameRate, source: usize, cut: i64, dur: i64, (in_
 }
 
 pub(crate) fn composition(name: &str, rate: FrameRate, tracks: Vec<CTrack>) -> Composition {
-    Composition { name: name.into(), rate, sample_rate: 48_000, width: 1920, height: 1080, start_tc: 0, drop: false, tracks, markers: Vec::new() }
+    Composition {
+        name: name.into(),
+        aaf_mob_id: None,
+        rate,
+        sample_rate: 48_000,
+        width: 1920,
+        height: 1080,
+        start_tc: 0,
+        drop: false,
+        tracks,
+        markers: Vec::new(),
+    }
 }
 
 pub(crate) fn track(kind: CKind, name: &str, number: u32, items: Vec<CItem>) -> CTrack {