diff --git a/t/flow.t b/t/flow.t
index 4a6162d84..4d7ee5ca2 100644
--- a/t/flow.t
+++ b/t/flow.t
@@ -22,8 +22,8 @@ use Slic3r::Test;
     $config->set('bottom_solid_layers', 1);
     $config->set('first_layer_extrusion_width', 2);
     $config->set('first_layer_height', '100%');
-    $config->set('filament_diameter', 3.0);
-    $config->set('nozzle_diameter', 0.5);
+    $config->set('filament_diameter', [ 3.0 ]);
+    $config->set('nozzle_diameter', [ 0.5 ]);
     
     my $print = Slic3r::Test::init_print('20mm_cube', config => $config);
     my @E_per_mm = ();
diff --git a/t/shells.t b/t/shells.t
index bdd9c65bf..dc38ff4aa 100644
--- a/t/shells.t
+++ b/t/shells.t
@@ -148,8 +148,8 @@ use Slic3r::Test;
     $config->set('solid_infill_speed', 99);
     $config->set('top_solid_infill_speed', 99);
     $config->set('bridge_speed', 99);
-    $config->set('filament_diameter', 3.0);
-    $config->set('nozzle_diameter', 0.5);
+    $config->set('filament_diameter', [ 3.0 ]);
+    $config->set('nozzle_diameter', [ 0.5 ]);
 
     my $print = Slic3r::Test::init_print('sloping_hole', config => $config);
     my %solid_layers = ();  # Z => 1