diff --git a/include/blt/iterator/iterator.h b/include/blt/iterator/iterator.h
index 48c1070..b758417 100644
--- a/include/blt/iterator/iterator.h
+++ b/include/blt/iterator/iterator.h
@@ -22,6 +22,7 @@
 #include <blt/iterator/common.h>
 #include <blt/iterator/zip.h>
 #include <blt/iterator/enumerate.h>
+#include <blt/iterator/flatten.h>
 #include <type_traits>
 #include <iterator>
 #include <tuple>