diff --git a/actix-server/CHANGES.md b/actix-server/CHANGES.md
index 067adcd6..7111fb0b 100644
--- a/actix-server/CHANGES.md
+++ b/actix-server/CHANGES.md
@@ -1,5 +1,11 @@
 # Changes
 
+## Unreleased
+
+### Changed
+
+* workers must be greater than 0
+
 ## [1.0.3] - 2020-05-19
 
 ### Changed
diff --git a/actix-server/src/builder.rs b/actix-server/src/builder.rs
index f3f6ad86..8a90d598 100644
--- a/actix-server/src/builder.rs
+++ b/actix-server/src/builder.rs
@@ -72,8 +72,9 @@ impl ServerBuilder {
     /// Set number of workers to start.
     ///
     /// By default server uses number of available logical cpu as workers
-    /// count.
+    /// count. Workers must be greater than 0.
     pub fn workers(mut self, num: usize) -> Self {
+        assert_ne!(num, 0, "workers must be greater than 0");
         self.threads = num;
         self
     }