diff --git a/seinflux.py b/seinflux.py
index d950812..9773117 100644
--- a/seinflux.py
+++ b/seinflux.py
@@ -141,6 +141,8 @@ class SEHistory(InfluxDBWrapper):
                     table = result.get(final_key)
                     if table is None:
                         result[final_key] = table = Table(tags, merge_key[0], ('_time', primary))
+                    else:
+                        table.tags.update(tags)  # for previously undefined units
                     by_idx[col_idx] = table
                 for row in rows:
                     by_idx[row[2]].append((row[0], row[1]))
@@ -334,7 +336,7 @@ class SEHistory(InfluxDBWrapper):
                         chunks = current.setdefault(devcombi, [])
                         if chunks and time.localtime(chunks[-1][0])[:3] == time.localtime(ts)[:3]:
                             # merge when started at the same day
-                            chunk = chunks[-1][1]
+                            chunk = chunks[-1]
                             chunk[1] = ETERNITY
                         else:
                             chunk = [ts, ETERNITY]