diff --git a/lib/Slic3r/Extruder.pm b/lib/Slic3r/Extruder.pm
index 3f06cd641..8ab9c2790 100644
--- a/lib/Slic3r/Extruder.pm
+++ b/lib/Slic3r/Extruder.pm
@@ -9,11 +9,11 @@ has 'extrusion_multiplier'      => (is => 'rw', required => 1);
 has 'temperature'               => (is => 'rw', required => 1);
 has 'first_layer_temperature'   => (is => 'rw', required => 1);
 
-has 'e_per_mmc'             => (is => 'rw');
+has 'e_per_mm3'                 => (is => 'rw');
 
 sub BUILD {
     my $self = shift;
-    $self->e_per_mmc(
+    $self->e_per_mm3(
         $Slic3r::scaling_factor
         * $self->extrusion_multiplier
         * (4 / (($self->filament_diameter ** 2) * PI))
diff --git a/lib/Slic3r/Flow.pm b/lib/Slic3r/Flow.pm
index 23468254b..f73fa7b22 100644
--- a/lib/Slic3r/Flow.pm
+++ b/lib/Slic3r/Flow.pm
@@ -43,7 +43,7 @@ sub BUILD {
         $min_flow_spacing = $flow_width - $self->layer_height * (1 - PI/4);
     } else {
         # rectangle with shrunk semicircles at the ends
-        $min_flow_spacing = $flow_width * (1 - PI/4) + $self->nozzle_diameter * PI/4;
+        $min_flow_spacing = $self->nozzle_diameter * (1 - PI/4) + $flow_width * PI/4;
     }
     $flow_spacing = $flow_width - $Slic3r::overlap_factor * ($flow_width - $min_flow_spacing);
     
diff --git a/lib/Slic3r/GCode.pm b/lib/Slic3r/GCode.pm
index f8a96e93c..06cb652d9 100644
--- a/lib/Slic3r/GCode.pm
+++ b/lib/Slic3r/GCode.pm
@@ -162,7 +162,7 @@ sub extrude_path {
     my $h = $path->depth_layers * $self->layer->height;
     my $w = ($s - ($self->layer ? $self->layer->flow->min_spacing : $Slic3r::flow->min_spacing) * $Slic3r::overlap_factor) / (1 - $Slic3r::overlap_factor);
     
-    my $area;
+    my $area; # = mm^3 of extrudate per mm of tool movement 
     if ($path->role == EXTR_ROLE_BRIDGE) {
         $area = ($s**2) * PI/4;
     } elsif ($w >= ($self->extruder->nozzle_diameter + $h)) {
@@ -173,7 +173,7 @@ sub extrude_path {
         $area = $self->extruder->nozzle_diameter * $h * (1 - PI/4) + $h * $w * PI/4;
     }
     
-    my $e = $self->extruder->e_per_mmc * $area;
+    my $e = $self->extruder->e_per_mm3 * $area;
     
     # extrude arc or line
     $self->speed( $role_speeds{$path->role} || die "Unknown role: " . $path->role );