diff --git a/dist/index.js b/dist/index.js
index fae00d4..fc7d10b 100644
--- a/dist/index.js
+++ b/dist/index.js
@@ -395,6 +395,23 @@ const toolCache = __importStar(__nccwpck_require__(7784));
 const gpg = __importStar(__nccwpck_require__(9787));
 const base_1 = __nccwpck_require__(5686);
 class VerifyingToolchainInstaller extends base_1.ToolchainInstaller {
+    get signatureUrl() {
+        return `${this.baseUrl}/${this.data.download_signature}`;
+    }
+    downloadSignature() {
+        return __awaiter(this, void 0, void 0, function* () {
+            try {
+                return yield toolCache.downloadTool(this.signatureUrl);
+            }
+            catch (error) {
+                if (error instanceof toolCache.HTTPError &&
+                    error.httpStatusCode === 404) {
+                    return undefined;
+                }
+                throw error;
+            }
+        });
+    }
     download() {
         const _super = Object.create(null, {
             download: { get: () => super.download }
@@ -405,9 +422,11 @@ class VerifyingToolchainInstaller extends base_1.ToolchainInstaller {
             const [, toolchain, signature] = yield Promise.all([
                 gpg.setupKeys(),
                 _super.download.call(this),
-                toolCache.downloadTool(sigUrl)
+                this.downloadSignature()
             ]);
-            yield gpg.verify(signature, toolchain);
+            if (signature) {
+                yield gpg.verify(signature, toolchain);
+            }
             return toolchain;
         });
     }
diff --git a/package.json b/package.json
index 1ec103a..bb2b647 100644
--- a/package.json
+++ b/package.json
@@ -8,13 +8,13 @@
   "license": "MIT",
   "homepage": "https://github.com/SwiftyLab/setup-swift#readme",
   "swiftorg": {
-    "commit": "332574c8459304994580ac67605a8891d01da580",
+    "commit": "8485bd396d05e3a021c9b905d4f48ba204d1f589",
     "release": {
-      "name": 5.9,
-      "tag": "swift-5.9-RELEASE",
+      "name": "5.9.1",
+      "tag": "swift-5.9.1-RELEASE",
       "xcode": "Xcode 15",
-      "xcode_release": true,
-      "date": "2023-09-18T00:00:00.000Z",
+      "xcode_release": false,
+      "date": "2023-10-19T00:00:00.000Z",
       "platforms": [
         {
           "name": "Ubuntu 18.04",
@@ -24,7 +24,7 @@
         },
         {
           "name": "Ubuntu 20.04",
-          "docker": "5.9-focal",
+          "docker": "5.9.1-focal",
           "archs": [
             "x86_64",
             "aarch64"
@@ -32,7 +32,7 @@
         },
         {
           "name": "Ubuntu 22.04",
-          "docker": "5.9-jammy",
+          "docker": "5.9.1-jammy",
           "archs": [
             "x86_64",
             "aarch64"
@@ -40,14 +40,14 @@
         },
         {
           "name": "CentOS 7",
-          "docker": "5.9-centos7",
+          "docker": "5.9.1-centos7",
           "archs": [
             "x86_64"
           ]
         },
         {
           "name": "Amazon Linux 2",
-          "docker": "5.9-amazonlinux2",
+          "docker": "5.9.1-amazonlinux2",
           "archs": [
             "x86_64",
             "aarch64"
@@ -55,7 +55,7 @@
         },
         {
           "name": "Red Hat Universal Base Image 9",
-          "docker": "5.9-rhel-ubi9",
+          "docker": "5.9.1-rhel-ubi9",
           "dir": "ubi9",
           "archs": [
             "x86_64",
@@ -72,12 +72,12 @@
     },
     "dev": {
       "name": "5.10",
-      "date": "2023-09-09T16:10:00.000Z",
-      "tag": "swift-5.10-DEVELOPMENT-SNAPSHOT-2023-09-09-a"
+      "date": "2023-10-24T16:10:00.000Z",
+      "tag": "swift-5.10-DEVELOPMENT-SNAPSHOT-2023-10-24-a"
     },
     "snapshot": {
-      "date": "2023-09-23T16:10:00.000Z",
-      "tag": "swift-DEVELOPMENT-SNAPSHOT-2023-09-23-a"
+      "date": "2023-10-24T16:10:00.000Z",
+      "tag": "swift-DEVELOPMENT-SNAPSHOT-2023-10-24-a"
     }
   },
   "engines": {
diff --git a/src/installer/verify.ts b/src/installer/verify.ts
index 820f2a8..b75a856 100644
--- a/src/installer/verify.ts
+++ b/src/installer/verify.ts
@@ -7,15 +7,35 @@ import {SignedToolchainSnapshot} from '../snapshot'
 export abstract class VerifyingToolchainInstaller<
   Snapshot extends SignedToolchainSnapshot
 > extends ToolchainInstaller<Snapshot> {
+  private get signatureUrl() {
+    return `${this.baseUrl}/${this.data.download_signature}`
+  }
+
+  private async downloadSignature() {
+    try {
+      return await toolCache.downloadTool(this.signatureUrl)
+    } catch (error) {
+      if (
+        error instanceof toolCache.HTTPError &&
+        error.httpStatusCode === 404
+      ) {
+        return undefined
+      }
+      throw error
+    }
+  }
+
   protected async download() {
     const sigUrl = `${this.baseUrl}/${this.data.download_signature}`
     core.debug(`Downloading snapshot signature from "${sigUrl}"`)
     const [, toolchain, signature] = await Promise.all([
       gpg.setupKeys(),
       super.download(),
-      toolCache.downloadTool(sigUrl)
+      this.downloadSignature()
     ])
-    await gpg.verify(signature, toolchain)
+    if (signature) {
+      await gpg.verify(signature, toolchain)
+    }
     return toolchain
   }
 }
diff --git a/swiftorg b/swiftorg
index 332574c..8485bd3 160000
--- a/swiftorg
+++ b/swiftorg
@@ -1 +1 @@
-Subproject commit 332574c8459304994580ac67605a8891d01da580
+Subproject commit 8485bd396d05e3a021c9b905d4f48ba204d1f589