diff --git a/CHTCollectionViewWaterfallLayout.m b/CHTCollectionViewWaterfallLayout.m
index e1ce651..194659f 100644
--- a/CHTCollectionViewWaterfallLayout.m
+++ b/CHTCollectionViewWaterfallLayout.m
@@ -193,13 +193,6 @@ - (id)initWithCoder:(NSCoder *)aDecoder {
 #pragma mark - Methods to Override
 - (void)prepareLayout {
   [super prepareLayout];
-    
-  [self.headersAttribute removeAllObjects];
-  [self.footersAttribute removeAllObjects];
-  [self.unionRects removeAllObjects];
-  [self.columnHeights removeAllObjects];
-  [self.allItemAttributes removeAllObjects];
-  [self.sectionItemAttributes removeAllObjects];
 
   NSInteger numberOfSections = [self.collectionView numberOfSections];
   if (numberOfSections == 0) {
@@ -212,6 +205,13 @@ - (void)prepareLayout {
   // Initialize variables
   NSInteger idx = 0;
 
+  [self.headersAttribute removeAllObjects];
+  [self.footersAttribute removeAllObjects];
+  [self.unionRects removeAllObjects];
+  [self.columnHeights removeAllObjects];
+  [self.allItemAttributes removeAllObjects];
+  [self.sectionItemAttributes removeAllObjects];
+
   for (NSInteger section = 0; section < numberOfSections; section++) {
     NSInteger columnCount = [self columnCountForSection:section];
     NSMutableArray *sectionColumnHeights = [NSMutableArray arrayWithCapacity:columnCount];