diff --git a/src-python/apngasm_python/_apngasm_python/__init__.pyi b/src-python/apngasm_python/_apngasm_python/__init__.pyi
index 8cdc3fc..b65241b 100644
--- a/src-python/apngasm_python/_apngasm_python/__init__.pyi
+++ b/src-python/apngasm_python/_apngasm_python/__init__.pyi
@@ -477,7 +477,7 @@ def create_frame_from_rgb(pixels: numpy.typing.NDArray, width: int, height: int,
     :param numpy.typing.NDArray pixels: The RGB pixel data, expressed as 3D numpy array.
     :param int width: The width of the pixel data.
     :param int height: The height of the pixel data.
-    :param numpy.typing.NDArray trns_color: The color [r, g, b] to be treated as transparent, expressed as 1D numpy array.
+    :param Optional[numpy.typing.NDArray] trns_color: The color [r, g, b] to be treated as transparent, expressed as 1D numpy array.
     :param int delay_num: The delay numerator for this frame (defaults to DEFAULT_FRAME_NUMERATOR).
     :param int delay_den: The delay denominator for this frame (defaults to DEFAULT_FRAME_DENMINATOR).