diff --git a/packages/web-api/src/WebClient.spec.js b/packages/web-api/src/WebClient.spec.js
index 8bbb1b297..8d452e7e0 100644
--- a/packages/web-api/src/WebClient.spec.js
+++ b/packages/web-api/src/WebClient.spec.js
@@ -1143,6 +1143,7 @@ describe('WebClient', function () {
       client.apiCall('method')
         .catch((err) => {
           assert.instanceOf(err, Error);
+          assert.include(err.message, 'retry-after header: notanumber', 'Raw retry-after header value included in error');
           scope.done();
           done();
         });
diff --git a/packages/web-api/src/WebClient.ts b/packages/web-api/src/WebClient.ts
index 2ec81c499..521725918 100644
--- a/packages/web-api/src/WebClient.ts
+++ b/packages/web-api/src/WebClient.ts
@@ -414,7 +414,7 @@ export class WebClient extends Methods {
             throw Error(`A rate limit was exceeded (url: ${url}, retry-after: ${retrySec})`);
           } else {
             // TODO: turn this into some CodedError
-            throw new AbortError(new Error(`Retry header did not contain a valid timeout (url: ${url})`));
+            throw new AbortError(new Error(`Retry header did not contain a valid timeout (url: ${url}, retry-after header: ${response.headers['retry-after']})`));
           }
         }