diff --git a/README.md b/README.md
index 0933c307..5bd2bdba 100644
--- a/README.md
+++ b/README.md
@@ -46,6 +46,9 @@ signAddon(
     // WebExtensions do not require an ID.
     // See the notes below about dealing with IDs.
     id: 'your-addon-id@somewhere',
+    // The release channel (listed or unlisted).
+    // Default: most recently used channel.
+    channel: undefined,
     // Save downloaded files to this directory.
     // Default: current working directory.
     downloadDir: undefined,
diff --git a/src/amo-client.js b/src/amo-client.js
index 407b72ee..f9ca68a4 100644
--- a/src/amo-client.js
+++ b/src/amo-client.js
@@ -77,12 +77,13 @@ export class Client {
    *   - `xpiPath` Path to xpi file.
    *   - `guid` Optional add-on GUID, aka the ID in install.rdf.
    *   - `version` add-on version string.
+   *   - `channel` release channel (listed, unlisted).
    * @return {Promise} signingResult with keys:
    *   - success: boolean
    *   - downloadedFiles: Array of file objects
    *   - id: string identifier for the signed add-on
    */
-  sign({guid, version, xpiPath}) {
+  sign({guid, version, channel=null, xpiPath}) {
 
     const formData = {
       upload: this._fs.createReadStream(xpiPath),
@@ -93,6 +94,9 @@ export class Client {
       // PUT to a specific URL for this add-on + version.
       addonUrl += encodeURIComponent(guid) +
         "/versions/" + encodeURIComponent(version) + "/";
+      if (channel) {
+        formData.channel = channel;
+      }
     } else {
       // POST to a generic URL to create a new add-on.
       this.debug("Signing add-on without an ID");
diff --git a/src/index.js b/src/index.js
index bc7e52d1..da128ea4 100644
--- a/src/index.js
+++ b/src/index.js
@@ -14,6 +14,9 @@ export default function signAddon(
     id,
     // The add-on version number for AMO.
     version,
+    // The release channel on AMO (listed or unlisted).
+    // Defaults to most recently used channel.
+    channel=null,
     // Your API key (JWT issuer) from AMO Devhub.
     apiKey,
     // Your API secret (JWT secret) from AMO Devhub.
@@ -87,6 +90,7 @@ export default function signAddon(
         xpiPath: xpiPath,
         guid: id,
         version: version,
+        channel: channel,
       });
 
     });
diff --git a/tests/test.amo-client.js b/tests/test.amo-client.js
index e9aaa032..5c26890e 100644
--- a/tests/test.amo-client.js
+++ b/tests/test.amo-client.js
@@ -138,6 +138,8 @@ describe("amoClient.Client", function() {
         expect(putCall.conf.formData.upload).to.be.equal("fake-read-stream");
         // When doing a PUT, the version is in the URL not the form data.
         expect(putCall.conf.formData.version).to.be.undefined;
+        // When no channel is supplied, the API is expected to use the most recent channel.
+        expect(putCall.conf.formData.channel).to.be.undefined;
 
         expect(waitForSignedAddon.called).to.be.equal(true);
         expect(waitForSignedAddon.firstCall.args[0])
@@ -171,6 +173,80 @@ describe("amoClient.Client", function() {
         expect(call.conf.url).to.match(/\/addons\/$/);
         expect(call.conf.formData.upload).to.be.equal("fake-read-stream");
         expect(call.conf.formData.version).to.be.equal(conf.version);
+        // Channel is not a valid parameter for new add-ons.
+        expect(call.conf.formData.channel).to.be.undefined;
+
+        expect(waitForSignedAddon.called).to.be.equal(true);
+        expect(waitForSignedAddon.firstCall.args[0])
+          .to.be.equal(apiStatusUrl);
+      });
+    });
+
+    it("lets you sign an unlisted add-on", function() {
+      var apiStatusUrl = "https://api/addon/version/upload/abc123";
+      var conf = {
+        guid: "a-guid",
+        version: "a-version",
+        channel: "unlisted",
+      };
+      var waitForSignedAddon = sinon.spy(() => {});
+      this.client.waitForSignedAddon = waitForSignedAddon;
+
+      this.client._request = new MockRequest({
+        httpResponse: {statusCode: 202},
+        // Partial response like:
+        // http://olympia.readthedocs.org/en/latest/topics/api/signing.html#checking-the-status-of-your-upload
+        responseBody: {
+          url: apiStatusUrl,
+        },
+      });
+
+      return this.sign(conf).then(() => {
+        var putCall = this.client._request.calls[0];
+        expect(putCall.name).to.be.equal("put");
+
+        var partialUrl = "/addons/" + conf.guid + "/versions/" + conf.version;
+        expect(putCall.conf.url).to.include(partialUrl);
+        expect(putCall.conf.formData.upload).to.be.equal("fake-read-stream");
+        // When doing a PUT, the version is in the URL not the form data.
+        expect(putCall.conf.formData.version).to.be.undefined;
+        expect(putCall.conf.formData.channel).to.be.equal("unlisted");
+
+        expect(waitForSignedAddon.called).to.be.equal(true);
+        expect(waitForSignedAddon.firstCall.args[0])
+          .to.be.equal(apiStatusUrl);
+      });
+    });
+
+    it("lets you sign a listed add-on", function() {
+      var apiStatusUrl = "https://api/addon/version/upload/abc123";
+      var conf = {
+        guid: "a-guid",
+        version: "a-version",
+        channel: "listed",
+      };
+      var waitForSignedAddon = sinon.spy(() => {});
+      this.client.waitForSignedAddon = waitForSignedAddon;
+
+      this.client._request = new MockRequest({
+        httpResponse: {statusCode: 202},
+        // Partial response like:
+        // http://olympia.readthedocs.org/en/latest/topics/api/signing.html#checking-the-status-of-your-upload
+        responseBody: {
+          url: apiStatusUrl,
+        },
+      });
+
+      return this.sign(conf).then(() => {
+        var putCall = this.client._request.calls[0];
+        expect(putCall.name).to.be.equal("put");
+
+        var partialUrl = "/addons/" + conf.guid + "/versions/" + conf.version;
+        expect(putCall.conf.url).to.include(partialUrl);
+        expect(putCall.conf.formData.upload).to.be.equal("fake-read-stream");
+        // When doing a PUT, the version is in the URL not the form data.
+        expect(putCall.conf.formData.version).to.be.undefined;
+        expect(putCall.conf.formData.channel).to.be.equal("listed");
 
         expect(waitForSignedAddon.called).to.be.equal(true);
         expect(waitForSignedAddon.firstCall.args[0])
diff --git a/tests/test.sign.js b/tests/test.sign.js
index 46fcb88f..a05649fd 100644
--- a/tests/test.sign.js
+++ b/tests/test.sign.js
@@ -97,6 +97,16 @@ describe("sign", function() {
     });
   });
 
+  it("passes release channel to the signer", () => {
+    const channel = "listed";
+    return runSignCmd({
+      cmdOptions: {channel},
+    }).then(function() {
+      expect(signingCall.called).to.be.equal(true);
+      expect(signingCall.firstCall.args[0].channel).to.be.equal(channel);
+    });
+  });
+
   it("passes JWT expiration to the signing client", () => {
     const expiresIn = 60 * 15; // 15 minutes
     return runSignCmd({