diff --git a/python/cudf/cudf/core/resample.py b/python/cudf/cudf/core/resample.py
index 2bed71ea751..57630e7d4a9 100644
--- a/python/cudf/cudf/core/resample.py
+++ b/python/cudf/cudf/core/resample.py
@@ -1,4 +1,4 @@
-# SPDX-FileCopyrightText: Copyright (c) 2021 NVIDIA CORPORATION &
+# SPDX-FileCopyrightText: Copyright (c) 2021-2022, NVIDIA CORPORATION &
 # AFFILIATES. All rights reserved.  SPDX-License-Identifier:
 # Apache-2.0
 #
diff --git a/python/dask_cudf/dask_cudf/groupby.py b/python/dask_cudf/dask_cudf/groupby.py
index a64aabe1a6b..22705c2b83b 100644
--- a/python/dask_cudf/dask_cudf/groupby.py
+++ b/python/dask_cudf/dask_cudf/groupby.py
@@ -245,6 +245,7 @@ def last(self, split_every=None, split_out=1):
     def aggregate(self, arg, split_every=None, split_out=1):
         if arg == "size":
             return self.size()
+
         arg = _redirect_aggs(arg)
 
         if _groupby_supported(self) and _aggs_supported(arg, SUPPORTED_AGGS):
@@ -431,6 +432,7 @@ def last(self, split_every=None, split_out=1):
     def aggregate(self, arg, split_every=None, split_out=1):
         if arg == "size":
             return self.size()
+
         arg = _redirect_aggs(arg)
 
         if not isinstance(arg, dict):
@@ -503,7 +505,7 @@ def groupby_agg(
     if isinstance(gb_cols, str):
         gb_cols = [gb_cols]
     columns = [c for c in ddf.columns if c not in gb_cols]
-    if isinstance(aggs, list):
+    if not isinstance(aggs, dict):
         aggs = {col: aggs for col in columns}
 
     # Assert if our output will have a MultiIndex; this will be the case if
@@ -665,6 +667,8 @@ def _aggs_supported(arg, supported: set):
             _global_set = set(arg)
 
         return bool(_global_set.issubset(supported))
+    elif isinstance(arg, str):
+        return arg in supported
     return False
 
 
diff --git a/python/dask_cudf/dask_cudf/tests/test_groupby.py b/python/dask_cudf/dask_cudf/tests/test_groupby.py
index 5aa9cffb789..2b7f2bdae36 100644
--- a/python/dask_cudf/dask_cudf/tests/test_groupby.py
+++ b/python/dask_cudf/dask_cudf/tests/test_groupby.py
@@ -58,7 +58,10 @@ def test_groupby_basic(series, aggregation):
     "func",
     [
         lambda df: df.groupby("x").agg({"y": "max"}),
+        lambda df: df.groupby("x").agg(["sum", "max"]),
         lambda df: df.groupby("x").y.agg(["sum", "max"]),
+        lambda df: df.groupby("x").agg("sum"),
+        lambda df: df.groupby("x").y.agg("sum"),
     ],
 )
 def test_groupby_agg(func):
@@ -663,11 +666,20 @@ def test_groupby_agg_redirect(aggregations):
 
 
 @pytest.mark.parametrize(
-    "arg",
-    [["not_supported"], {"a": "not_supported"}, {"a": ["not_supported"]}],
+    "arg,supported",
+    [
+        ("sum", True),
+        (["sum"], True),
+        ({"a": "sum"}, True),
+        ({"a": ["sum"]}, True),
+        ("not_supported", False),
+        (["not_supported"], False),
+        ({"a": "not_supported"}, False),
+        ({"a": ["not_supported"]}, False),
+    ],
 )
-def test_is_supported(arg):
-    assert _aggs_supported(arg, {"supported"}) is False
+def test_is_supported(arg, supported):
+    assert _aggs_supported(arg, SUPPORTED_AGGS) is supported
 
 
 def test_groupby_unique_lists():