diff --git a/lib/Slic3r.pm b/lib/Slic3r.pm
index 792cad87a..4cea239b0 100644
--- a/lib/Slic3r.pm
+++ b/lib/Slic3r.pm
@@ -15,9 +15,10 @@ sub debugf {
 }
 
 # load threads before Moo as required by it
+our $have_threads;
 BEGIN {
     use Config;
-    our $have_threads = $Config{useithreads} && eval "use threads; use Thread::Queue; 1";
+    $have_threads = $Config{useithreads} && eval "use threads; use Thread::Queue; 1";
 }
 
 use Moo;