diff --git a/src/fontconfig/fontconfig.pyx b/src/fontconfig/fontconfig.pyx
index 7002d83..8caa8ba 100644
--- a/src/fontconfig/fontconfig.pyx
+++ b/src/fontconfig/fontconfig.pyx
@@ -2,7 +2,6 @@ import atexit
 import logging
 from typing import Any, Dict, Iterable, Iterator, List, Tuple
 
-from cython.cimports.libc.stdlib import free
 cimport fontconfig._fontconfig as c_impl
 
 
@@ -239,10 +238,9 @@ cdef class Config:
     def font_sort(self, p: Pattern, trim: bool) -> Optional[FontSet]:
         """Return list of matching fonts"""
         cdef c_impl.FcResult result
-        cdef c_impl.FcCharSet* csp = NULL
         cdef c_impl.FcFontSet* ptr = c_impl.FcFontSort(
-            self._ptr, p._ptr, <c_impl.FcBool>trim, &csp, &result)
-        # TODO: Return csp
+            self._ptr, p._ptr, <c_impl.FcBool>trim, NULL, &result)
+        # TODO: Support csp
         if result == c_impl.FcResultMatch:
             return FontSet(<intptr_t>ptr)
         elif result == c_impl.FcResultNoMatch:
@@ -513,9 +511,12 @@ cdef class Pattern:
         if result is NULL:
             raise ValueError("Invalid format: %s" % fmt)
         py_str = <bytes>(result).decode("utf-8")
-        free(result)
+        c_impl.FcStrFree(result)
         return py_str
 
+    def __repr__(self) -> str:
+        return dict(self).__repr__()
+
 
 cdef void _ObjectToFcValue(object value, c_impl.FcValue* fc_value):
     assert fc_value is not NULL
@@ -676,7 +677,13 @@ cdef class ObjectSet:
 
     def add(self, value: str) -> bool:
         """Add to an object set"""
-        return c_impl.FcObjectSetAdd(self._ptr, value.encode("utf-8"))
+        cdef bytes value_ = value.encode("utf-8")
+        cdef c_impl.FcObjectType* object_type = c_impl.FcNameGetObjectType(value_)
+        if object_type is NULL:
+            raise KeyError("Invalid value: %s" % value)
+        elif object_type.type == c_impl.FcTypeUnknown:
+            raise KeyError("Unknown value: %s" % value)
+        return <bint>c_impl.FcObjectSetAdd(self._ptr, value_)
 
     def build(self, values: Iterable[str]) -> None:
         """Build object set from iterable"""
@@ -684,6 +691,23 @@ cdef class ObjectSet:
             if not self.add(value):
                 raise MemoryError()
 
+    def __iter__(self) -> Iterator[str]:
+        for i in range(self._ptr.nobject):
+            yield <bytes>(self._ptr.objects[i]).decode("utf-8")
+
+    def __repr__(self) -> str:
+        return list(self).__repr__()
+
+    def __len__(self) -> int:
+        return self._ptr.nobject
+
+    def __getitem__(self, index: int) -> str:
+        if index >= self._ptr.nobject or index <= -self._ptr.nobject:
+            raise IndexError("Invalid index: %d" % index)
+        if index < 0:
+            index += self._ptr.nobject
+        return <bytes>(self._ptr.objects[index]).decode("utf-8")
+
 
 cdef class FontSet:
     """A FontSet simply holds a list of patterns; these are used to return
@@ -723,6 +747,19 @@ cdef class FontSet:
         for i in range(self._ptr.nfont):
             yield Pattern(<intptr_t>(self._ptr.fonts[i]), owner=False)
 
+    def __repr__(self) -> str:
+        return list(self).__repr__()
+
+    def __len__(self) -> int:
+        return self._ptr.nfont
+
+    def __getitem__(self, index: int) -> Pattern:
+        if index >= self._ptr.nfont or index <= -self._ptr.nfont:
+            raise IndexError("Invalid index: %d" % index)
+        if index < 0:
+            index += self._ptr.nfont
+        return Pattern(<intptr_t>self._ptr.fonts[index], owner=False)
+
 
 def query(where: str = "", select: Iterable[str] = ("family",)) -> List[Dict[str, Any]]:
     """
diff --git a/tests/test_fontconfig.py b/tests/test_fontconfig.py
index 2203605..d0f8145 100644
--- a/tests/test_fontconfig.py
+++ b/tests/test_fontconfig.py
@@ -247,10 +247,6 @@ def test_Pattern_remove() -> None:
     assert isinstance(pattern.remove("aspect", 0), bool)
 
 
-def test_Pattern_iter(pattern: fontconfig.Pattern) -> None:
-    dict(pattern)
-
-
 def test_Pattern_unparse(pattern: fontconfig.Pattern) -> None:
     assert isinstance(pattern.unparse(), str)
 
@@ -263,6 +259,14 @@ def test_Pattern_default_format(pattern: fontconfig.Pattern) -> None:
     assert isinstance(pattern.format("%{lang}"), str)
 
 
+def test_Pattern_iter(pattern: fontconfig.Pattern) -> None:
+    dict(pattern)
+
+
+def test_Pattern_repr(pattern) -> None:
+    repr(pattern)
+
+
 @pytest.fixture
 def object_set():
     object_set = fontconfig.ObjectSet.create()
@@ -270,6 +274,25 @@ def object_set():
     yield object_set
 
 
+def test_ObjectSet_add(object_set) -> None:
+    assert isinstance(object_set.add("familylang"), bool)
+
+
+def test_ObjectSet_iter(object_set) -> None:
+    for item in object_set:
+        assert isinstance(item, str)
+
+
+def test_ObjectSet_getitem(object_set) -> None:
+    for i in range(len(object_set)):
+        assert isinstance(object_set[i], str)
+    assert isinstance(object_set[-1], str)
+
+
+def test_ObjectSet_repr(object_set) -> None:
+    repr(object_set)
+
+
 def test_query() -> None:
     result = fontconfig.query(
         where=":lang=en:family=Arial",