diff --git a/stix2/properties.py b/stix2/properties.py
index 5de7a1e..f4060e5 100644
--- a/stix2/properties.py
+++ b/stix2/properties.py
@@ -183,11 +183,12 @@ class CallableValues(list):
 class StringProperty(Property):
 
     def __init__(self, **kwargs):
-        self.string_type = text_type
         super(StringProperty, self).__init__(**kwargs)
 
     def clean(self, value):
-        return self.string_type(value)
+        if not isinstance(value, string_types):
+            return text_type(value)
+        return value
 
 
 class TypeProperty(Property):
@@ -439,21 +440,22 @@ class EnumProperty(StringProperty):
         super(EnumProperty, self).__init__(**kwargs)
 
     def clean(self, value):
-        value = super(EnumProperty, self).clean(value)
-        if value not in self.allowed:
-            raise ValueError("value '{}' is not valid for this enumeration.".format(value))
-        return self.string_type(value)
+        cleaned_value = super(EnumProperty, self).clean(value)
+        if cleaned_value not in self.allowed:
+            raise ValueError("value '{}' is not valid for this enumeration.".format(cleaned_value))
+
+        return cleaned_value
 
 
 class PatternProperty(StringProperty):
 
     def clean(self, value):
-        str_value = super(PatternProperty, self).clean(value)
-        errors = run_validator(str_value)
+        cleaned_value = super(PatternProperty, self).clean(value)
+        errors = run_validator(cleaned_value)
         if errors:
             raise ValueError(str(errors[0]))
 
-        return self.string_type(value)
+        return cleaned_value
 
 
 class ObservableProperty(Property):
diff --git a/stix2/test/v21/test_markings.py b/stix2/test/v21/test_markings.py
index a7dff22..bd247e6 100644
--- a/stix2/test/v21/test_markings.py
+++ b/stix2/test/v21/test_markings.py
@@ -76,7 +76,7 @@ EXPECTED_CAMPAIGN_WITH_GRANULAR_REF_MARKINGS = """{
 }"""
 
 
-EXPECTED_CAMPAIGN_WITH_GRANULAR_LANG_MARKINGS = """{
+EXPECTED_CAMPAIGN_WITH_GRANULAR_LANG_MARKINGS = u"""{
     "type": "campaign",
     "spec_version": "2.1",
     "id": "campaign--8e2e2d2b-17d4-4cbf-938f-98ee46b3cd3f",
diff --git a/stix2/test/v21/test_properties.py b/stix2/test/v21/test_properties.py
index 298a8df..e4fa4a0 100644
--- a/stix2/test/v21/test_properties.py
+++ b/stix2/test/v21/test_properties.py
@@ -450,6 +450,11 @@ def test_enum_property_valid(value):
     assert enum_prop.clean('b')
 
 
+def test_enum_property_clean():
+    enum_prop = EnumProperty(['1'])
+    assert enum_prop.clean(1) == '1'
+
+
 def test_enum_property_invalid():
     enum_prop = EnumProperty(['a', 'b', 'c'])
     with pytest.raises(ValueError):