diff --git a/pcbnew/zone_filler.cpp b/pcbnew/zone_filler.cpp
index 2f6c07635f..3c76d3bb03 100644
--- a/pcbnew/zone_filler.cpp
+++ b/pcbnew/zone_filler.cpp
@@ -191,16 +191,16 @@ bool ZONE_FILLER::Fill( std::vector<ZONE_CONTAINER*> aZones, bool aCheck )
 
     for( auto& zone : toFill )
     {
-        // Non-net zones do not have islands by definition
-        if( zone.m_zone->GetNetCode() <= 0 )
-            continue;
-
         std::sort( zone.m_islands.begin(), zone.m_islands.end(), std::greater<int>() );
         SHAPE_POLY_SET poly = zone.m_zone->GetFilledPolysList();
 
-        for( auto idx : zone.m_islands )
+        // only zones with net code > 0 can have islands to remove by definition
+        if( zone.m_zone->GetNetCode() > 0 )
         {
-            poly.DeletePolygon( idx );
+            for( auto idx : zone.m_islands )
+            {
+                poly.DeletePolygon( idx );
+            }
         }
 
         zone.m_zone->SetFilledPolysList( poly );