diff --git a/pyerrors/pyerrors.py b/pyerrors/pyerrors.py
index db70dfaa..ba913ad8 100644
--- a/pyerrors/pyerrors.py
+++ b/pyerrors/pyerrors.py
@@ -78,7 +78,7 @@ class Obs:
                     if len(dc) == 1:
                         self.idl[name] = range(idx[0], idx[-1] + dc[0], dc[0])
                     else:
-                        self.idl[name] = np.array(idx, dtype=_type_chooser(len(idx)))
+                        self.idl[name] = list(idx)
                 else:
                     raise Exception('incompatible type for idl[%s].' % (name))
         else:
@@ -1467,10 +1467,3 @@ def merge_obs(list_of_obs):
     o.is_merged = np.any([oi.is_merged for oi in list_of_obs])
     o.reweighted = np.max([oi.reweighted for oi in list_of_obs])
     return o
-
-
-def _type_chooser(n):
-    for dtype in [np.uint8, np.uint16, np.uint32, np.uint64]:
-        if n <= dtype(-1):
-            return dtype
-    raise Exception('{} is really big!'.format(n))