diff --git a/ixmp/core.py b/ixmp/core.py
index e2e069588..abd4b2a8d 100644
--- a/ixmp/core.py
+++ b/ixmp/core.py
@@ -562,11 +562,11 @@ def add_set(self, name, key, comment=None):
             idx_names = self.idx_names(name)
             if "comment" in list(key):
                 for i in key.index:
-                    jSet.addElement(to_jlist(key.ix[i], idx_names),
+                    jSet.addElement(to_jlist(key.iloc[i], idx_names),
                                     str(key['comment'][i]))
             else:
                 for i in key.index:
-                    jSet.addElement(to_jlist(key.ix[i], idx_names))
+                    jSet.addElement(to_jlist(key.iloc[i], idx_names))
         elif isinstance(key, list):
             if isinstance(key[0], list):
                 for i in range(len(key)):
@@ -677,13 +677,13 @@ def add_par(self, name, key, val=None, unit=None, comment=None):
             idx_names = self.idx_names(name)
             if "comment" in list(key):
                 for i in key.index:
-                    jPar.addElement(to_jlist(key.ix[i], idx_names),
+                    jPar.addElement(to_jlist(key.iloc[i], idx_names),
                                     _jdouble(key['value'][i]),
                                     str(key['unit'][i]),
                                     str(key['comment'][i]))
             else:
                 for i in key.index:
-                    jPar.addElement(to_jlist(key.ix[i], idx_names),
+                    jPar.addElement(to_jlist(key.iloc[i], idx_names),
                                     _jdouble(key['value'][i]),
                                     str(key['unit'][i]))
         elif isinstance(key, list) and isinstance(key[0], list):
@@ -1108,7 +1108,7 @@ def _removeElement(jItem, key):
                 key = pd.DataFrame.from_dict(key, orient='columns', dtype=None)
             idx_names = to_pylist(jItem.getIdxNames())
             for i in key.index:
-                jItem.removeElement(to_jlist(key.ix[i], idx_names))
+                jItem.removeElement(to_jlist(key.iloc[i], idx_names))
         else:
             jItem.removeElement(str(key))