diff --git a/lib/Slic3r/Layer/BridgeDetector.pm b/lib/Slic3r/Layer/BridgeDetector.pm
index ccb4119ea..54e4c9b4d 100644
--- a/lib/Slic3r/Layer/BridgeDetector.pm
+++ b/lib/Slic3r/Layer/BridgeDetector.pm
@@ -89,16 +89,16 @@ sub detect_angle {
                 my $my_anchors      = [ map $_->clone, @$anchors ];
                 
                 # rotate everything - the center point doesn't matter
-                $_->rotate($angle, [0,0]) for @$my_clip_area, @$my_anchors;
+                $_->rotate(-$angle, [0,0]) for @$my_clip_area, @$my_anchors;
             
                 # generate lines in this direction
                 my $bounding_box = Slic3r::Geometry::BoundingBox->new_from_points([ map @$_, map @$_, @$my_anchors ]);
             
                 my @lines = ();
-                for (my $x = $bounding_box->x_min; $x <= $bounding_box->x_max; $x += $line_increment) {
+                for (my $y = $bounding_box->y_min; $y <= $bounding_box->y_max; $y+= $line_increment) {
                     push @lines, Slic3r::Polyline->new(
-                        [$x, $bounding_box->y_min + scaled_epsilon],
-                        [$x, $bounding_box->y_max - scaled_epsilon],
+                        [$bounding_box->x_min, $y],
+                        [$bounding_box->x_max, $y],
                     );
                 }
                 
@@ -143,7 +143,7 @@ sub detect_angle {
     }
     
     if (defined $self->angle) {
-        if ($self->angle >= PI - epsilon) {
+        if ($self->angle >= PI) {
             $self->angle($self->angle - PI);
         }
         
diff --git a/t/bridges.t b/t/bridges.t
index 557175f2f..ff20af2fe 100644
--- a/t/bridges.t
+++ b/t/bridges.t
@@ -30,8 +30,8 @@ use Slic3r::Test;
         ok check_angle([$lower], $bridge, $expected_angle, $tolerance), 'correct bridge angle for O-shaped overhang';
     };
 
-    $test->([20,10], 0, 0);
-    $test->([10,20], 0, 90);
+    $test->([20,10], 0, 90);
+    $test->([10,20], 0, 0);
     $test->([20,10], 45, 135, 20);
     $test->([20,10], 135, 45, 20);
 }
@@ -81,7 +81,10 @@ sub check_angle {
     
     # our epsilon is equal to the steps used by the bridge detection algorithm
     ###use XXX; YYY [ rad2deg($result), $expected ];
-    return defined $result && abs(rad2deg($result) - $expected) < $tolerance;
+    # returned value must be non-negative, check for that too
+    my $delta=rad2deg($result) - $expected;
+    $delta-=180 if $delta>=180 - epsilon;
+    return defined $result && $result>=0 && abs($delta) < $tolerance;
 }
 
 __END__