diff --git a/pcbnew/exporters/step/exporter_step.cpp b/pcbnew/exporters/step/exporter_step.cpp
index aae0f88f7e..2bc9557aed 100644
--- a/pcbnew/exporters/step/exporter_step.cpp
+++ b/pcbnew/exporters/step/exporter_step.cpp
@@ -469,6 +469,7 @@ void EXPORTER_STEP::calculatePcbThickness()
                 break;
 
             case BS_ITEM_TYPE_COPPER:
+            case BS_ITEM_TYPE_SOLDERMASK:
                 if( item->IsEnabled() )
                     thickness += item->GetThickness();