diff --git a/client/client_test.go b/client/client_test.go
index dc47c089e..4bdc9c1c9 100644
--- a/client/client_test.go
+++ b/client/client_test.go
@@ -42,6 +42,7 @@ func TestClientIntegration(t *testing.T) {
 		testOCIExporter,
 		testWhiteoutParentDir,
 		testDuplicateWhiteouts,
+		testSchema1Image,
 	})
 }
 
@@ -686,6 +687,24 @@ func testWhiteoutParentDir(t *testing.T, sb integration.Sandbox) {
 	require.True(t, ok)
 }
 
+// #296
+func testSchema1Image(t *testing.T, sb integration.Sandbox) {
+	t.Parallel()
+	c, err := New(sb.Address())
+	require.NoError(t, err)
+	defer c.Close()
+
+	st := llb.Image("gcr.io/google_containers/pause:3.0@sha256:0d093c962a6c2dd8bb8727b661e2b5f13e9df884af9945b4cc7088d9350cd3ee")
+
+	def, err := st.Marshal()
+	require.NoError(t, err)
+
+	err = c.Solve(context.TODO(), def, SolveOpt{}, nil)
+	require.NoError(t, err)
+
+	checkAllReleasable(t, c, sb, true)
+}
+
 func requiresLinux(t *testing.T) {
 	if runtime.GOOS != "linux" {
 		t.Skipf("unsupported GOOS: %s", runtime.GOOS)
diff --git a/source/containerimage/pull.go b/source/containerimage/pull.go
index a351b73a2..1f28dc8cd 100644
--- a/source/containerimage/pull.go
+++ b/source/containerimage/pull.go
@@ -240,9 +240,9 @@ func (p *puller) Snapshot(ctx context.Context) (cache.ImmutableRef, error) {
 
 		handlers := []images.Handler{
 			images.HandlerFunc(func(ctx context.Context, desc ocispec.Descriptor) ([]ocispec.Descriptor, error) {
-				usedBlobs = append(usedBlobs, desc)
 				mu.Lock()
 				defer mu.Unlock()
+				usedBlobs = append(usedBlobs, desc)
 				delete(allBlobs, desc.Digest)
 				return nil, nil
 			}),