diff --git a/transport/src/main/java/io/netty/bootstrap/ServerBootstrap.java b/transport/src/main/java/io/netty/bootstrap/ServerBootstrap.java
index 33e388a8c0..4dc95a4dff 100644
--- a/transport/src/main/java/io/netty/bootstrap/ServerBootstrap.java
+++ b/transport/src/main/java/io/netty/bootstrap/ServerBootstrap.java
@@ -241,6 +241,9 @@ public final class ServerBootstrap extends AbstractBootstrap<ServerBootstrap, Se
             logger.warn("childGroup is not set. Using parentGroup instead.");
             childGroup = group();
         }
+        if (channelFactory == null) {
+            throw new IllegalStateException("factory not set");
+        }
         return this;
     }