diff --git a/adafruit_ssd1608.py b/adafruit_ssd1608.py
index a0db119..9110761 100644
--- a/adafruit_ssd1608.py
+++ b/adafruit_ssd1608.py
@@ -48,7 +48,7 @@
 class SSD1608(displayio.EPaperDisplay):
     """SSD1608 driver"""
 
-    def __init__(self, bus, **kwargs):
+    def __init__(self, bus: displayio.FourWire, **kwargs) -> None:
         start_sequence = bytearray(_START_SEQUENCE)
         width = kwargs["width"]
         start_sequence[4] = (width - 1) & 0xFF