diff --git a/py_src/sphn/__init__.pyi b/py_src/sphn/__init__.pyi
index 0fd3c71..63ee64a 100644
--- a/py_src/sphn/__init__.pyi
+++ b/py_src/sphn/__init__.pyi
@@ -70,7 +70,7 @@ def write_wav(filename, data, sample_rate):
     pass
 
 class FileReader:
-    def __init__(path):
+    def __init__(self, path):
         pass
 
     @property
@@ -121,7 +121,7 @@ class FileReader:
         pass
 
 class OpusStreamReader:
-    def __init__(sample_rate):
+    def __init__(self, sample_rate):
         pass
 
     def append_bytes(self, data):
@@ -145,7 +145,7 @@ class OpusStreamReader:
         pass
 
 class OpusStreamWriter:
-    def __init__(sample_rate):
+    def __init__(self, sample_rate):
         pass
 
     def append_pcm(self, pcm):
diff --git a/stub.py b/stub.py
index d7b906c..18bfdf4 100644
--- a/stub.py
+++ b/stub.py
@@ -108,7 +108,10 @@ def pyi_file(obj, indent=""):
 
         # Init
         if obj.__text_signature__:
-            body += f"{indent}def __init__{obj.__text_signature__}:\n"
+            ts = obj.__text_signature__
+            if len(ts) > 1 and ts.startswith("(") and not ts.startswith("(self"):
+                ts = "(self, " + ts[1:]
+            body += f"{indent}def __init__{ts}:\n"
             body += f"{indent+INDENT}pass\n"
             body += "\n"