diff --git a/stix2/test/v20/test_bundle.py b/stix2/test/v20/test_bundle.py
index 806421a..57c189e 100644
--- a/stix2/test/v20/test_bundle.py
+++ b/stix2/test/v20/test_bundle.py
@@ -332,4 +332,4 @@ def test_bundle_getitem_overload_obj_id_not_found():
 
     with pytest.raises(KeyError) as excinfo:
         bundle['non existent']
-    assert "neither a valid bundle property nor does it match the id property" in str(excinfo.value)
+    assert "neither a property on the bundle nor does it match the id property" in str(excinfo.value)
diff --git a/stix2/test/v21/test_bundle.py b/stix2/test/v21/test_bundle.py
index 4f33fb5..47d0a7a 100644
--- a/stix2/test/v21/test_bundle.py
+++ b/stix2/test/v21/test_bundle.py
@@ -306,4 +306,4 @@ def test_bundle_getitem_overload_obj_id_not_found():
 
     with pytest.raises(KeyError) as excinfo:
         bundle['non existent']
-    assert "neither a valid bundle property nor does it match the id property" in str(excinfo.value)
+    assert "neither a property on the bundle nor does it match the id property" in str(excinfo.value)
diff --git a/stix2/v20/bundle.py b/stix2/v20/bundle.py
index dd2bb2c..be419da 100644
--- a/stix2/v20/bundle.py
+++ b/stix2/v20/bundle.py
@@ -52,4 +52,4 @@ class Bundle(_STIXBase):
             try:
                 return self.get_obj(key)
             except KeyError:
-                raise KeyError("'%s' is neither a valid bundle property nor does it match the id property of any of the bundle's objects" % key)
+                raise KeyError("'%s' is neither a property on the bundle nor does it match the id property of any of the bundle's objects" % key)
diff --git a/stix2/v21/bundle.py b/stix2/v21/bundle.py
index 352cf3b..3ed6024 100644
--- a/stix2/v21/bundle.py
+++ b/stix2/v21/bundle.py
@@ -50,4 +50,4 @@ class Bundle(_STIXBase):
             try:
                 return self.get_obj(key)
             except KeyError:
-                raise KeyError("'%s' is neither a valid bundle property nor does it match the id property of any of the bundle's objects" % key)
+                raise KeyError("'%s' is neither a property on the bundle nor does it match the id property of any of the bundle's objects" % key)