diff --git a/CCHMapClusterController/CCHMapClusterController.m b/CCHMapClusterController/CCHMapClusterController.m
index d6ee90c..e57bd8e 100644
--- a/CCHMapClusterController/CCHMapClusterController.m
+++ b/CCHMapClusterController/CCHMapClusterController.m
@@ -217,20 +217,28 @@ - (void)updateDebugPolygonsInGridMapRect:(MKMapRect)gridMapRect withCellMapSize:
             }
         }
     }
-    
-    // Add polygons outlining each cell
-    CCHMapClusterControllerEnumerateCells(gridMapRect, cellMapSize, ^(MKMapRect cellMapRect) {
-        //        cellMapRect.origin.x -= MKMapSizeWorld.width;  // fixes issue when view port spans 180th meridian
-        
-        MKMapPoint points[4];
-        points[0] = MKMapPointMake(MKMapRectGetMinX(cellMapRect), MKMapRectGetMinY(cellMapRect));
-        points[1] = MKMapPointMake(MKMapRectGetMaxX(cellMapRect), MKMapRectGetMinY(cellMapRect));
-        points[2] = MKMapPointMake(MKMapRectGetMaxX(cellMapRect), MKMapRectGetMaxY(cellMapRect));
-        points[3] = MKMapPointMake(MKMapRectGetMinX(cellMapRect), MKMapRectGetMaxY(cellMapRect));
-        CCHMapClusterControllerDebugPolygon *debugPolygon = (CCHMapClusterControllerDebugPolygon *)[CCHMapClusterControllerDebugPolygon polygonWithPoints:points count:4];
-        debugPolygon.mapClusterController = self;
-        [mapView addOverlay:debugPolygon];
-    });
+
+    int yCells = ceil((MKMapRectGetHeight(gridMapRect) + 0.1)/cellMapSize);
+    int xCells = ceil((MKMapRectGetWidth(gridMapRect) + 0.1)/cellMapSize);
+    MKMapPoint points[yCells * 3 + 1 + xCells * 3 + 1];
+    int pointCount = 0;
+    points[pointCount++] = MKMapPointMake(MKMapRectGetMinX(gridMapRect), MKMapRectGetMinY(gridMapRect));
+    for (double x = MKMapRectGetMinX(gridMapRect); x <= MKMapRectGetMaxX(gridMapRect)+0.1; x += cellMapSize) {
+        points[pointCount++] = MKMapPointMake(x, MKMapRectGetMinY(gridMapRect));
+        points[pointCount++] = MKMapPointMake(x, MKMapRectGetMaxY(gridMapRect));
+        points[pointCount++] = MKMapPointMake(x, MKMapRectGetMinY(gridMapRect));
+    }
+
+    points[pointCount++] = MKMapPointMake(MKMapRectGetMinX(gridMapRect), MKMapRectGetMinY(gridMapRect));
+    for (double y = MKMapRectGetMinY(gridMapRect); y <= MKMapRectGetMaxY(gridMapRect)+0.1; y += cellMapSize) {
+        points[pointCount++] = MKMapPointMake(MKMapRectGetMinX(gridMapRect), y);
+        points[pointCount++] = MKMapPointMake(MKMapRectGetMaxX(gridMapRect), y);
+        points[pointCount++] = MKMapPointMake(MKMapRectGetMinX(gridMapRect), y);
+    }
+
+    CCHMapClusterControllerDebugPolygon *debugPolygon = (CCHMapClusterControllerDebugPolygon *)[CCHMapClusterControllerDebugPolygon polygonWithPoints:points count:pointCount];
+    debugPolygon.mapClusterController = self;
+    [mapView addOverlay:debugPolygon];
 }
 
 - (void)deselectAllAnnotations
diff --git a/CCHMapClusterController/CCHMapClusterControllerUtils.m b/CCHMapClusterController/CCHMapClusterControllerUtils.m
index f19159f..bad02b3 100644
--- a/CCHMapClusterController/CCHMapClusterControllerUtils.m
+++ b/CCHMapClusterController/CCHMapClusterControllerUtils.m
@@ -43,6 +43,11 @@ MKMapRect CCHMapClusterControllerAlignMapRectToCellSize(MKMapRect mapRect, doubl
     double endX = ceil(MKMapRectGetMaxX(mapRect) / cellSize) * cellSize;
     double endY = ceil(MKMapRectGetMaxY(mapRect) / cellSize) * cellSize;
     
+    if (startX >= MKMapSizeWorld.width) {
+        startX -= MKMapSizeWorld.width;
+        endX -= MKMapSizeWorld.width;
+    }
+    
     return MKMapRectMake(startX, startY, endX - startX, endY - startY);
 }
 
@@ -321,4 +326,4 @@ BOOL CCHMapClusterControllerIsUniqueLocation(NSSet *annotations)
     }
     
     return (geohash != nil);
-}
\ No newline at end of file
+}
diff --git a/CCHMapClusterController/CCHMapViewDelegateProxy.m b/CCHMapClusterController/CCHMapViewDelegateProxy.m
index c57956c..be8516d 100644
--- a/CCHMapClusterController/CCHMapViewDelegateProxy.m
+++ b/CCHMapClusterController/CCHMapViewDelegateProxy.m
@@ -137,6 +137,26 @@ - (MKOverlayView *)mapView:(MKMapView *)mapView viewForOverlay:(id<MKOverlay>)ov
     
     return view;
 }
+
+- (MKOverlayRenderer *)mapView:(MKMapView *)mapView rendererForOverlay:(id<MKOverlay>)overlay
+{
+    MKOverlayRenderer *renderer;
+	
+    // Target can override return value
+    if ([self.target respondsToSelector:@selector(mapView:rendererForOverlay:)]) {
+        renderer = [self.target mapView:mapView rendererForOverlay:overlay];
+    }
+	
+    // Default return value for debug polygons
+    if (renderer == nil && [overlay isKindOfClass:CCHMapClusterControllerDebugPolygon.class]) {
+        MKPolygonRenderer *polygonRenderer = [[MKPolygonRenderer alloc] initWithPolygon:(MKPolygon *)overlay];
+        polygonRenderer.strokeColor = [UIColor.blueColor colorWithAlphaComponent:0.7];
+        polygonRenderer.lineWidth = 1;
+        renderer = polygonRenderer;
+    }
+    
+    return renderer;
+}
 #else
 - (MKOverlayRenderer *)mapView:(MKMapView *)mapView rendererForOverlay:(id<MKOverlay>)overlay
 {