diff --git a/py2wasm/python.py b/py2wasm/python.py
index 77b53d2..6f5d36b 100644
--- a/py2wasm/python.py
+++ b/py2wasm/python.py
@@ -45,6 +45,11 @@ class Visitor:
                     function_body_map[stmt] = wnode
                 continue
 
+            if isinstance(stmt, ast.ClassDef):
+                wclass = self.pre_visit_ClassDef(module, stmt)
+                module.classes.append(wclass)
+                continue
+
             # No other pre visits to do
 
         for stmt in node.body:
@@ -54,6 +59,9 @@ class Visitor:
                 # else: It's an import, no actual body to parse
                 continue
 
+            if isinstance(stmt, ast.ClassDef):
+                continue
+
             raise NotImplementedError(stmt)
 
         return module
@@ -70,8 +78,6 @@ class Visitor:
 
         Nested / dynamicly created functions are not yet supported
         """
-        del module
-
         exported = False
 
         if node.decorator_list:
@@ -108,13 +114,22 @@ class Visitor:
         assert not node.args.kwarg
         assert not node.args.defaults
 
-        params = [
-            (a.arg, _parse_annotation(a.annotation), )
-            for a in [
-                *node.args.posonlyargs,
-                *node.args.args,
-            ]
-        ]
+        class_lookup = {
+            x.name: x
+            for x in module.classes
+        }
+
+        params = []
+        for arg in [*node.args.posonlyargs, *node.args.args]:
+            if not isinstance(arg.annotation, ast.Name):
+                raise NotImplementedError
+
+            print(class_lookup)
+            print(arg.annotation.id)
+            if arg.annotation.id in class_lookup:
+                params.append((arg.arg, arg.annotation.id, ))
+            else:
+                params.append((arg.arg, _parse_annotation(arg.annotation), ))
 
         return wasm.Function(node.name, exported, params, result, [])
 
@@ -137,6 +152,51 @@ class Visitor:
 
         func.statements = statements
 
+    def pre_visit_ClassDef(
+            self,
+            module: wasm.Module,
+            node: ast.ClassDef,
+        ) -> wasm.Class:
+        """
+        TODO: Document this
+        """
+        del module
+
+        if node.bases or node.keywords or node.decorator_list:
+            raise NotImplementedError
+
+        members: List[wasm.ClassMember] = []
+
+        for stmt in node.body:
+            if not isinstance(stmt, ast.AnnAssign):
+                raise NotImplementedError
+
+            if not isinstance(stmt.target, ast.Name):
+                raise NotImplementedError
+
+            if not isinstance(stmt.annotation, ast.Name):
+                raise NotImplementedError
+
+            if stmt.annotation.id != 'i32':
+                raise NotImplementedError
+
+            if stmt.value is None:
+                default = None
+            else:
+                if not isinstance(stmt.value, ast.Constant):
+                    raise NotImplementedError
+
+                if not isinstance(stmt.value.value, int):
+                    raise NotImplementedError
+
+                default = wasm.Constant(stmt.value.value)
+
+            members.append(wasm.ClassMember(
+                stmt.target.id, stmt.annotation.id, default
+            ))
+
+        return wasm.Class(node.name, members)
+
     def visit_stmt(
             self,
             module: wasm.Module,
@@ -235,6 +295,9 @@ class Visitor:
         if isinstance(node, ast.Name):
             return self.visit_Name(wlocals, exp_type, node)
 
+        if isinstance(node, ast.Attribute):
+            return [] # TODO
+
         raise NotImplementedError(node)
 
     def visit_UnaryOp(
@@ -331,10 +394,11 @@ class Visitor:
 
         called_name = node.func.id
 
-        search_list: List[Union[wasm.Function, wasm.Import]]
+        search_list: List[Union[wasm.Function, wasm.Import, wasm.Class]]
         search_list = [
             *module.functions,
             *module.imports,
+            *module.classes,
         ]
 
         called_func_list = [
@@ -346,8 +410,15 @@ class Visitor:
         assert 1 == len(called_func_list), \
             'Could not find function {}'.format(node.func.id)
 
-        called_params = called_func_list[0].params
-        called_result = called_func_list[0].result
+        if isinstance(called_func_list[0], wasm.Class):
+            called_params = [
+                (x.name, x.type, )
+                for x in called_func_list[0].members
+            ]
+            called_result: Optional[str] = called_func_list[0].name
+        else:
+            called_params = called_func_list[0].params
+            called_result = called_func_list[0].result
 
         assert exp_type == called_result
 
@@ -471,5 +542,5 @@ def _parse_annotation(ann: Optional[ast.expr]) -> str:
     assert ann is not None, 'Web Assembly requires type annotations'
     assert isinstance(ann, ast.Name)
     result = ann.id
-    assert result in ['i32', 'i64', 'f32', 'f64']
+    assert result in ['i32', 'i64', 'f32', 'f64'], result
     return result
diff --git a/py2wasm/wasm.py b/py2wasm/wasm.py
index 24d1f46..68300fc 100644
--- a/py2wasm/wasm.py
+++ b/py2wasm/wasm.py
@@ -2,7 +2,7 @@
 Python classes for storing the representation of Web Assembly code
 """
 
-from typing import Iterable, List, Optional, Tuple
+from typing import Iterable, List, Optional, Tuple, Union
 
 Param = Tuple[str, str]
 
@@ -83,6 +83,30 @@ class Function:
             '\n    '.join(x.generate() for x in self.statements),
         )
 
+class Constant:
+    """
+    TODO
+    """
+    def __init__(self, value: Union[None, bool, int, float]) -> None:
+        self.value = value
+
+class ClassMember:
+    """
+    Represents a Web Assembly class member
+    """
+    def __init__(self, name: str, type_: str, default: Optional[Constant]) -> None:
+        self.name = name
+        self.type = type_
+        self.default = default
+
+class Class:
+    """
+    Represents a Web Assembly class
+    """
+    def __init__(self, name: str, members: List[ClassMember]) -> None:
+        self.name = name
+        self.members = members
+
 class Module:
     """
     Represents a Web Assembly module
@@ -90,6 +114,7 @@ class Module:
     def __init__(self) -> None:
         self.imports: List[Import] = []
         self.functions: List[Function] = []
+        self.classes: List[Class] = []
 
     def generate(self) -> str:
         """
diff --git a/tests/integration/test_fib.py b/tests/integration/test_fib.py
index b27297d..bd701c9 100644
--- a/tests/integration/test_fib.py
+++ b/tests/integration/test_fib.py
@@ -28,3 +28,4 @@ def testEntry() -> i32:
     result = Suite(code_py, 'test_fib').run_code()
 
     assert 102334155 == result.returned_value
+    assert False
diff --git a/tests/integration/test_simple.py b/tests/integration/test_simple.py
index 7650c6c..c399e86 100644
--- a/tests/integration/test_simple.py
+++ b/tests/integration/test_simple.py
@@ -234,3 +234,40 @@ def helper(left: i32, right: i32) -> i32:
 
     assert 7 == result.returned_value
     assert [] == result.log_int32_list
+
+@pytest.mark.integration_test
+def test_assign():
+    code_py = """
+
+@exported
+def testEntry() -> i32:
+    a: i32 = 8947
+    return a
+"""
+
+    result = Suite(code_py, 'test_call').run_code()
+
+    assert 8947 == result.returned_value
+    assert [] == result.log_int32_list
+
+@pytest.mark.integration_test
+def test_struct():
+    code_py = """
+
+class Rectangle:
+    height: i32
+    width: i32
+    border: i32 # = 5
+
+@exported
+def testEntry() -> i32:
+    return helper(Rectangle(100, 150, 2))
+
+def helper(shape: Rectangle) -> i32:
+    return shape.height + shape.width + shape.border
+"""
+
+    result = Suite(code_py, 'test_call').run_code()
+
+    assert 100 == result.returned_value
+    assert [] == result.log_int32_list