diff --git a/lib/Slic3r/Surface.pm b/lib/Slic3r/Surface.pm
index 238229bd0..a410a66cc 100644
--- a/lib/Slic3r/Surface.pm
+++ b/lib/Slic3r/Surface.pm
@@ -39,10 +39,12 @@ sub group {
 
 sub offset {
     my $self = shift;
-    return map (ref $self)->new(
-        expolygon => $_,
-        map { $_ => $self->$_ } qw(surface_type depth_layers bridge_angle),
-    ), $self->expolygon->offset_ex(@_);
+    return map {
+        (ref $self)->new(
+            expolygon => $_,
+            map { $_ => $self->$_ } qw(surface_type depth_layers bridge_angle),
+        )
+    } $self->expolygon->offset_ex(@_);
 }
 
 sub add_hole {