diff --git a/README.md b/README.md
index d16349b..3956c1b 100644
--- a/README.md
+++ b/README.md
@@ -199,7 +199,7 @@ assert a.dumps() == d
 The API to access enum members and their values is similar to that of the native Enum type in Python 3. Functionally, it's best comparable to the IntEnum type.
 
 ### Custom types
-You can implement your own types by subclassing `BaseType` or `RawType`, and adding them to your cstruct instance with `addtype(name, type)`
+You can implement your own types by subclassing `BaseType` or `RawType`, and adding them to your cstruct instance with `add_type(name, type)`
 
 ### Custom definition parsers
 Don't like the C-like definition syntax? Write your own syntax parser!
diff --git a/tests/test_basic.py b/tests/test_basic.py
index 3dd4afa..49f22c9 100644
--- a/tests/test_basic.py
+++ b/tests/test_basic.py
@@ -39,9 +39,9 @@ def test_type_resolve(cs: cstruct):
         cs.resolve("fake")
     assert "Unknown type" in str(excinfo.value)
 
-    cs.addtype("ref0", "uint32")
+    cs.add_type("ref0", "uint32")
     for i in range(1, 15):  # Recursion limit is currently 10
-        cs.addtype(f"ref{i}", f"ref{i - 1}")
+        cs.add_type(f"ref{i}", f"ref{i - 1}")
 
     with pytest.raises(ResolveError) as excinfo:
         cs.resolve("ref14")