diff --git a/instances-manager/Dockerfile b/instances-manager/Dockerfile
index 054b05e..e887ae2 100644
--- a/instances-manager/Dockerfile
+++ b/instances-manager/Dockerfile
@@ -4,5 +4,5 @@ WORKDIR /instances-manager/
 EXPOSE 33332
 
 COPY build/install/instances-manager/ /instances-manager/
-ENV instances_MANAGER_OPTS="-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=*:5005 -XX:MaxRAMPercentage=85"
+ENV INSTANCES_MANAGER_OPTS="-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=*:5005 -XX:MaxRAMPercentage=85"
 CMD ["/instances-manager/bin/instances-manager"]
\ No newline at end of file
diff --git a/instances-manager/src/main/kotlin/org/modelix/instancesmanager/ProxyServletWithWebsocketSupport.kt b/instances-manager/src/main/kotlin/org/modelix/instancesmanager/ProxyServletWithWebsocketSupport.kt
index 98bb600..14f15de 100644
--- a/instances-manager/src/main/kotlin/org/modelix/instancesmanager/ProxyServletWithWebsocketSupport.kt
+++ b/instances-manager/src/main/kotlin/org/modelix/instancesmanager/ProxyServletWithWebsocketSupport.kt
@@ -160,7 +160,7 @@ abstract class ProxyServletWithWebsocketSupport : ProxyServlet() {
                         }
                     }
 
-                    override fun onWebSocketClose(statusCode: Int, reason: String) {
+                    override fun onWebSocketClose(statusCode: Int, reason: String?) {
                         sessionA?.close(statusCode, reason)
                     }