diff --git a/lib/Slic3r.pm b/lib/Slic3r.pm
index 61df506e4e..f4ff98c899 100644
--- a/lib/Slic3r.pm
+++ b/lib/Slic3r.pm
@@ -3,7 +3,7 @@ package Slic3r;
 use strict;
 use warnings;
 
-our $VERSION = "0.5.6";
+our $VERSION = "0.5.7-beta";
 
 our $debug = 0;
 sub debugf {
diff --git a/lib/Slic3r/Fill/Concentric.pm b/lib/Slic3r/Fill/Concentric.pm
index c2d3142bbc..7bd01ba646 100644
--- a/lib/Slic3r/Fill/Concentric.pm
+++ b/lib/Slic3r/Fill/Concentric.pm
@@ -14,6 +14,9 @@ sub fill_surface {
     
     my $scaled_flow_width = scale $params{flow_width};
     my $distance = $scaled_flow_width / $params{density};
+    # TODO: adjust distance and flow width for solid surfaces
+    # using the same logic as Rectilinear infill
+    # (factor it out to parent class)
     
     my @contour_loops = ();
     my @hole_loops = ();
@@ -49,7 +52,7 @@ sub fill_surface {
         push @paths, $path->p;
     }
     
-    return @paths;
+    return {}, @paths;
 }
 
 1;