diff --git a/include/boost/histogram/dynamic_storage.hpp b/include/boost/histogram/dynamic_storage.hpp
index 561cc0cc..ad00025b 100644
--- a/include/boost/histogram/dynamic_storage.hpp
+++ b/include/boost/histogram/dynamic_storage.hpp
@@ -181,13 +181,14 @@ dynamic_storage& dynamic_storage::operator+=(const dynamic_storage& o)
       while (i--) {
         uint64_t n = 0;
         switch (o.depth()) {
+          case 0: /* nothing to do */ break;
           case sizeof(uint8_t) : n = o.buffer_.at<uint8_t> (i); break;
           case sizeof(uint16_t): n = o.buffer_.at<uint16_t>(i); break;
           case sizeof(uint32_t): n = o.buffer_.at<uint32_t>(i); break;
           case sizeof(uint64_t): n = o.buffer_.at<uint64_t>(i); break;
         }
         switch (buffer_.depth()) {
-          case 0: buffer_.depth(sizeof(uint8_t)); // fall through
+          case 0: buffer_.depth(sizeof(uint8_t)); // and fall through
           case sizeof(uint8_t) : add_impl<uint8_t> (buffer_, i, n); break;
           case sizeof(uint16_t): add_impl<uint16_t>(buffer_, i, n); break;
           case sizeof(uint32_t): add_impl<uint32_t>(buffer_, i, n); break;