diff --git a/actix-rt/src/runtime.rs b/actix-rt/src/runtime.rs
index e5269141..d98f85da 100644
--- a/actix-rt/src/runtime.rs
+++ b/actix-rt/src/runtime.rs
@@ -41,7 +41,7 @@ impl Error for RunError {
         self.inner.description()
     }
     fn cause(&self) -> Option<&Error> {
-        self.inner.cause()
+        self.inner.source()
     }
 }
 
diff --git a/actix-rt/src/system.rs b/actix-rt/src/system.rs
index 7fe31448..aaf15c7c 100644
--- a/actix-rt/src/system.rs
+++ b/actix-rt/src/system.rs
@@ -1,13 +1,13 @@
 use std::cell::RefCell;
 use std::io;
-use std::sync::atomic::{AtomicUsize, Ordering, ATOMIC_USIZE_INIT};
+use std::sync::atomic::{AtomicUsize, Ordering};
 
 use futures::sync::mpsc::UnboundedSender;
 
 use crate::arbiter::{Arbiter, SystemCommand};
 use crate::builder::{Builder, SystemRunner};
 
-static SYSTEM_COUNT: AtomicUsize = ATOMIC_USIZE_INIT;
+static SYSTEM_COUNT: AtomicUsize = AtomicUsize::new(0);
 
 /// System is a runtime manager.
 #[derive(Clone, Debug)]