diff --git a/xarray/core/combine.py b/xarray/core/combine.py
index 167b5a93ebc..e35bb51e030 100644
--- a/xarray/core/combine.py
+++ b/xarray/core/combine.py
@@ -248,7 +248,7 @@ def _combine_1d(
                 join=join,
             )
         except ValueError as err:
-            if "Encountered unexpected variable" in str(err):
+            if "encountered unexpected variable" in str(err):
                 raise ValueError(
                     "These objects cannot be combined using only "
                     "xarray.combine_nested, instead either use "
diff --git a/xarray/core/concat.py b/xarray/core/concat.py
index a5ec7c5185a..de0dfcc5a5d 100644
--- a/xarray/core/concat.py
+++ b/xarray/core/concat.py
@@ -374,7 +374,7 @@ def _dataset_concat(
     # check that global attributes are fixed across all datasets if necessary
     for ds in datasets[1:]:
         if compat == "identical" and not utils.dict_equiv(ds.attrs, result_attrs):
-            raise ValueError("Dataset global attributes are not equal.")
+            raise ValueError("Dataset global attributes not equal.")
 
     # we've already verified everything is consistent; now, calculate
     # shared dimension sizes so we can expand the necessary variables
diff --git a/xarray/tests/test_concat.py b/xarray/tests/test_concat.py
index 6142762063c..d624c5c1363 100644
--- a/xarray/tests/test_concat.py
+++ b/xarray/tests/test_concat.py
@@ -177,7 +177,7 @@ def test_concat_errors(self):
         with raises_regex(ValueError, "are not coordinates"):
             concat([data, data], "new_dim", coords=["not_found"])
 
-        with raises_regex(ValueError, "global attributes are not"):
+        with raises_regex(ValueError, "global attributes not"):
             data0, data1 = deepcopy(split_data)
             data1.attrs["foo"] = "bar"
             concat([data0, data1], "dim1", compat="identical")