diff --git a/pcbnew/router/pns_kicad_iface.cpp b/pcbnew/router/pns_kicad_iface.cpp
index e33f983b3e..33e63ea624 100644
--- a/pcbnew/router/pns_kicad_iface.cpp
+++ b/pcbnew/router/pns_kicad_iface.cpp
@@ -252,7 +252,23 @@ bool isCopper( const PNS::ITEM* aItem )
     if( parent && parent->Type() == PCB_PAD_T )
     {
         PAD* pad = static_cast<PAD*>( parent );
-        return pad->IsOnCopperLayer() && pad->GetAttribute() != PAD_ATTRIB::NPTH;
+
+        if( !pad->IsOnCopperLayer() )
+            return false;
+
+        if( pad->GetAttribute() != PAD_ATTRIB::NPTH )
+            return true;
+
+        // round NPTH with a hole size >= pad size are not on a copper layer
+        // All other NPTH are seen on copper layers
+        // This is a basic criteria, but probably enough for a NPTH
+        if( pad->GetShape() == PAD_SHAPE::CIRCLE )
+        {
+            if( pad->GetSize().x <= pad->GetDrillSize().x )
+                return false;
+        }
+
+        return true;
     }
 
     return true;