diff --git a/atom.go b/atom.go
index 1048b3a..df3a8cf 100644
--- a/atom.go
+++ b/atom.go
@@ -28,6 +28,7 @@ func parseAtom(data []byte, read *db) (*Feed, error) {
 	}
 	
 	out.Items = make([]*Item, 0, len(feed.Items))
+	out.ItemMap = make(map[string]struct{})
 	
 	// Process items.
 	for _, item := range feed.Items {
diff --git a/rss 1.0.go b/rss 1.0.go
index 75e324e..2748ae7 100644
--- a/rss 1.0.go	
+++ b/rss 1.0.go	
@@ -60,6 +60,7 @@ func parseRSS1(data []byte, read *db) (*Feed, error) {
 	}
 	
 	out.Items = make([]*Item, 0, len(feed.Items))
+	out.ItemMap = make(map[string]struct{})
 	
 	// Process items.
 	for _, item := range feed.Items {