diff --git a/scilog/snippet.py b/scilog/snippet.py
index 4b82a9f..31a3586 100644
--- a/scilog/snippet.py
+++ b/scilog/snippet.py
@@ -5,12 +5,14 @@ from .utils import typename
 
 def typechecked(func):
     @functools.wraps(func)
-    def typechecked_call(*args, **kwargs):
-        func_types = get_type_hints(func)
-        for index, key in enumerate(func_types.keys()):
-            if key != "return":
-                assert func_types[key] == type(args[index+1]), f"{repr(func)} expected to receive input of type {func_types[key].__name__} but received {type(args[index+1]).__name__}"
-        return func(*args, **kwargs)
+    def typechecked_call(obj, *args, **kwargs):
+        type_hints = get_type_hints(func)
+        del type_hints["return"]
+        for arg, dtype in zip(args, type_hints):
+            arg_type = type(arg)
+            if dtype != arg_type:
+                raise TypeError(f"{func} expected to receive input of type {dtype.__name__} but received {arg_type.__name__}")
+        return func(obj, *args, **kwargs)
     return typechecked_call