diff --git a/.github/workflows/docker.yml b/.github/workflows/docker.yml
index 5aa0818..f3d53d8 100644
--- a/.github/workflows/docker.yml
+++ b/.github/workflows/docker.yml
@@ -60,6 +60,11 @@ jobs:
           if [[ "$GITHUB_REF_NAME" == "main" ]]; then
             version="$base_version"
           elif [[ "$GITHUB_REF_NAME" == "dev" ]]; then
+            base_version="$(tr -d '[:space:]' < VERSION)"
+            if [[ ! "$base_version" =~ ^[0-9]+\.[0-9]+\.[0-9]+$ ]]; then
+              echo "Invalid development version: $base_version"
+              exit 1
+            fi
             version="$base_version-dev.$GITHUB_RUN_NUMBER"
           elif [[ "$GITHUB_REF" != refs/tags/v* ]]; then
             channel="${GITHUB_REF_NAME//[^0-9A-Za-z-]/-}"
diff --git a/VERSION b/VERSION
new file mode 100644
index 0000000..88c5fb8
--- /dev/null
+++ b/VERSION
@@ -0,0 +1 @@
+1.4.0
diff --git a/internal/sabr/multipart.go b/internal/sabr/multipart.go
index 3015cf6..59a4242 100644
--- a/internal/sabr/multipart.go
+++ b/internal/sabr/multipart.go
@@ -18,17 +18,28 @@ func downloadParts(
 	ctx, cancel := context.WithCancel(ctx)
 	defer cancel()
 	failures := make(chan error, parts)
-	var workers sync.WaitGroup
+	partJobs := make(chan int, parts)
 	for part := range parts {
+		partJobs <- part
+	}
+	close(partJobs)
+	var workers sync.WaitGroup
+	for range min(parts, maxConcurrentPartDownloads) {
 		workers.Add(1)
 		go func() {
 			defer workers.Done()
-			if err := downloadPart(ctx, client, options, part, parts, progress); err != nil {
-				select {
-				case failures <- err:
-				default:
+			for part := range partJobs {
+				if ctx.Err() != nil {
+					return
+				}
+				if err := downloadPart(ctx, client, options, part, parts, progress); err != nil {
+					select {
+					case failures <- err:
+					default:
+					}
+					cancel()
+					return
 				}
-				cancel()
 			}
 		}()
 	}
@@ -81,3 +92,5 @@ func downloadPart(
 	}
 	return closeTracks(tracks)
 }
+
+const maxConcurrentPartDownloads = 3
diff --git a/internal/sabr/multipart_test.go b/internal/sabr/multipart_test.go
new file mode 100644
index 0000000..e196124
--- /dev/null
+++ b/internal/sabr/multipart_test.go
@@ -0,0 +1,56 @@
+package sabr
+
+import (
+	"context"
+	"net/http"
+	"path/filepath"
+	"strconv"
+	"sync/atomic"
+	"testing"
+	"time"
+)
+
+func TestDownloadBoundsConcurrentSABRParts(t *testing.T) {
+	var active atomic.Int64
+	var peak atomic.Int64
+	var requests atomic.Int64
+	server := downloadTestServer(t, func(writer http.ResponseWriter, request *http.Request) {
+		current := active.Add(1)
+		defer active.Add(-1)
+		requests.Add(1)
+		for {
+			observed := peak.Load()
+			if current <= observed || peak.CompareAndSwap(observed, current) {
+				break
+			}
+		}
+		time.Sleep(20 * time.Millisecond)
+		part, err := strconv.Atoi(request.URL.Query().Get("part"))
+		if err != nil {
+			t.Error(err)
+			return
+		}
+		writeTestFrame(t, writer, frameInitialization, 140, 0, []byte("init"))
+		writeTestFrame(t, writer, frameMedia, 140, part+1, []byte("media"))
+		writeTestFrame(t, writer, frameComplete, 0, 0, nil)
+	})
+	defer server.Close()
+
+	output := filepath.Join(t.TempDir(), "audio.m4a")
+	err := Download(context.Background(), server.Client(), Options{
+		ManifestURL: server.URL,
+		AudioItag:   140,
+		AudioOnly:   true,
+		AudioPath:   output,
+		Parts:       maxDownloadParts,
+	}, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if requests.Load() != maxDownloadParts {
+		t.Fatalf("requests = %d, want %d", requests.Load(), maxDownloadParts)
+	}
+	if peak.Load() != maxConcurrentPartDownloads {
+		t.Fatalf("peak concurrency = %d, want %d", peak.Load(), maxConcurrentPartDownloads)
+	}
+}