diff --git a/basis/threads/threads.factor b/basis/threads/threads.factor
index af11d77f84..9d1cd29337 100644
--- a/basis/threads/threads.factor
+++ b/basis/threads/threads.factor
@@ -140,7 +140,11 @@ DEFER: next
     !
     ! And if sleep-time outputs f, there are no sleeping
     ! threads either... so WTF.
-    sleep-time [ die 0 ] unless* (sleep) next ;
+    sleep-time {
+        { [ dup not ] [ drop die ] }
+        { [ dup 0 = ] [ drop ] }
+        [ (sleep) ]
+    } cond next ;
 
 : (next) ( arg thread -- * )
     f >>state
diff --git a/core/io/streams/c/c.factor b/core/io/streams/c/c.factor
index 1da30fe922..cb978d5deb 100644
--- a/core/io/streams/c/c.factor
+++ b/core/io/streams/c/c.factor
@@ -73,7 +73,8 @@ M: c-io-backend init-io ;
 
 M: c-io-backend init-stdio init-c-stdio ;
 
-M: c-io-backend io-multiplex 60 60 * 1000 * 1000 * or (sleep) ;
+M: c-io-backend io-multiplex
+    dup 0 = [ drop ] [ 60 60 * 1000 * 1000 * or (sleep) ] if ;
 
 : fopen ( path mode -- alien )
     [ utf8 string>alien ] bi@ (fopen) ;