diff --git a/lib/Slic3r/Extruder.pm b/lib/Slic3r/Extruder.pm
index 4017b0e6b..ce4b706bb 100644
--- a/lib/Slic3r/Extruder.pm
+++ b/lib/Slic3r/Extruder.pm
@@ -119,9 +119,9 @@ sub extrude_path {
     
     # calculate extrusion length per distance unit
     my $s = $path->flow_spacing
-        || $path->role eq 'support-material'
+        || ($path->role eq 'support-material'
             ? ($Slic3r::flow_spacing * 1.5)
-            : $Slic3r::flow_spacing;
+            : $Slic3r::flow_spacing);
     my $h = $path->depth_layers * $self->layer->height;
     my $w = ($s - $Slic3r::min_flow_spacing * $Slic3r::overlap_factor) / (1 - $Slic3r::overlap_factor);