diff --git a/lib/Slic3r/Config.pm b/lib/Slic3r/Config.pm
index abf5b9093..aa645b99d 100644
--- a/lib/Slic3r/Config.pm
+++ b/lib/Slic3r/Config.pm
@@ -550,7 +550,7 @@ sub load {
         if ($key =~ /^(extrusion_width|bottom_layer_speed|first_layer_height)_ratio$/) {
             $key = $1;
             $key =~ s/^bottom_layer_speed$/first_layer_speed/;
-            $val = $val =~ /^\d+(\.\d+)?$/ ? ($val*100) . "%" : 0;
+            $val = $val =~ /^\d+(?:\.\d+)?$/ && $val != 0 ? ($val*100) . "%" : 0;
         }
         
         if (!exists $Options->{$key}) {
@@ -623,7 +623,7 @@ sub validate {
     }
     $Slic3r::perimeters_flow->calculate($Slic3r::perimeters_extrusion_width || $Slic3r::extrusion_width);
     $Slic3r::infill_flow->calculate($Slic3r::infill_extrusion_width || $Slic3r::extrusion_width);
-    Slic3r::debugf "Default flow width = %s, spacing = %s, min_spacing = %d\n",
+    Slic3r::debugf "Default flow width = %s, spacing = %s, min_spacing = %s\n",
         $Slic3r::flow->width, $Slic3r::flow->spacing, $Slic3r::flow->min_spacing;
     
     # --perimeters