diff --git a/pandas/core/groupby.py b/pandas/core/groupby.py
index 442f2132847ee..377f758926899 100644
--- a/pandas/core/groupby.py
+++ b/pandas/core/groupby.py
@@ -2790,6 +2790,10 @@ def true_and_notnull(x, *args, **kwargs):
     def nunique(self, dropna=True):
         """ Returns number of unique elements in the group """
         ids, _, _ = self.grouper.group_info
+        
+        if len(ids) == 0:  # bugfix for 12553
+            return Series([])
+        
         val = self.obj.get_values()
 
         try: