diff --git a/jedi/inference/value/instance.py b/jedi/inference/value/instance.py
index 8310e881..bc06cfd4 100644
--- a/jedi/inference/value/instance.py
+++ b/jedi/inference/value/instance.py
@@ -332,13 +332,14 @@ class TreeInstance(_BaseTreeInstance):
         for signature in self.class_value.py__getattribute__('__init__').get_signatures():
             # Just take the first result, it should always be one, because we
             # control the typeshed code.
-            if not signature.matches_signature(args) \
-                    or signature.value.tree_node is None:
+            funcdef = signature.value.tree_node
+            if funcdef is None or funcdef.type != 'funcdef' \
+                    or not signature.matches_signature(args):
                 # First check if the signature even matches, if not we don't
                 # need to infer anything.
                 continue
             bound_method = BoundMethod(self, self.class_value.as_context(), signature.value)
-            all_annotations = py__annotations__(signature.value.tree_node)
+            all_annotations = py__annotations__(funcdef)
             type_var_dict = infer_type_vars_for_execution(bound_method, args, all_annotations)
             if type_var_dict:
                 defined, = self.class_value.define_generics(
diff --git a/test/completion/classes.py b/test/completion/classes.py
index 04298aa3..5b7b42da 100644
--- a/test/completion/classes.py
+++ b/test/completion/classes.py
@@ -630,3 +630,19 @@ class C1(MyBase):
         self.f1() . # hey'''
         #? 13 MyBase.f1
         self.f1() . # hey'''
+
+# -----------------
+# With a very weird __init__
+# -----------------
+
+class WithWeirdInit:
+    class __init__:
+        def __init__(self, a):
+            self.a = a
+
+    def y(self):
+        return self.a
+
+
+#?
+WithWeirdInit(1).y()