diff --git a/content/local/locks.go b/content/local/locks.go
index d1d2d564d..077b6241e 100644
--- a/content/local/locks.go
+++ b/content/local/locks.go
@@ -41,7 +41,13 @@ func tryLock(ref string) error {
 	defer locksMu.Unlock()
 
 	if v, ok := locks[ref]; ok {
-		return errors.Wrapf(errdefs.ErrUnavailable, "ref %s locked since %s", ref, v.since)
+		// Returning the duration may help developers distinguish dead locks (long duration) from
+		// lock contentions (short duration).
+		now := time.Now()
+		return errors.Wrapf(
+			errdefs.ErrUnavailable,
+			"ref %s locked for %s (since %s)", ref, now.Sub(v.since), v.since,
+		)
 	}
 
 	locks[ref] = &lock{time.Now()}
diff --git a/content/local/locks_test.go b/content/local/locks_test.go
index c9d0034cc..3d1912dd5 100644
--- a/content/local/locks_test.go
+++ b/content/local/locks_test.go
@@ -28,5 +28,5 @@ func TestTryLock(t *testing.T) {
 	defer unlock("testref")
 
 	err = tryLock("testref")
-	assert.ErrorContains(t, err, "ref testref locked since ")
+	assert.ErrorContains(t, err, "ref testref locked for ")
 }