diff --git a/CHANGES.md b/CHANGES.md
index 6fe0174ad..ead69f293 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,9 +1,14 @@
 # Changes
 
 ## Unreleased - 2021-xx-xx
+### Added
+* `HttpServer::worker_max_blocking_threads` for setting block thread pool. [#2200]
+
 ### Changed
 * Update `language-tags` to `0.3`.
 
+[#2200]: https://github.com/actix/actix-web/pull/2200
+
 
 ## 4.0.0-beta.6 - 2021-04-17
 ### Added
diff --git a/src/server.rs b/src/server.rs
index 6e11c642f..44ae6f880 100644
--- a/src/server.rs
+++ b/src/server.rs
@@ -174,6 +174,16 @@ where
         self
     }
 
+    /// Set max number of threads for each worker's blocking task thread pool.
+    ///
+    /// One thread pool is set up **per worker**; not shared across workers.
+    ///
+    /// By default set to 512 / workers.
+    pub fn worker_max_blocking_threads(mut self, num: usize) -> Self {
+        self.builder = self.builder.worker_max_blocking_threads(num);
+        self
+    }
+
     /// Set server keep-alive setting.
     ///
     /// By default keep alive is set to a 5 seconds.