diff --git a/Tests/test_file_jpeg2k.py b/Tests/test_file_jpeg2k.py
index 5748fa5a1..01172fdbb 100644
--- a/Tests/test_file_jpeg2k.py
+++ b/Tests/test_file_jpeg2k.py
@@ -313,6 +313,18 @@ def test_rgba(ext: str) -> None:
         assert im.mode == "RGBA"
 
 
+def test_grayscale_four_channels() -> None:
+    with open("Tests/images/rgb_trns_ycbc.jp2", "rb") as fp:
+        data = fp.read()
+
+        # Change color space to OPJ_CLRSPC_GRAY
+        data = data[:76] + b"\x11" + data[77:]
+
+        with Image.open(BytesIO(data)) as im:
+            im.load()
+            assert im.mode == "RGBA"
+
+
 @pytest.mark.skipif(
     not os.path.exists(EXTRA_DIR), reason="Extra image files not installed"
 )
diff --git a/src/libImaging/Jpeg2KDecode.c b/src/libImaging/Jpeg2KDecode.c
index 4f185b529..cc6955ca5 100644
--- a/src/libImaging/Jpeg2KDecode.c
+++ b/src/libImaging/Jpeg2KDecode.c
@@ -615,6 +615,7 @@ static const struct j2k_decode_unpacker j2k_unpackers[] = {
     {"RGBA", OPJ_CLRSPC_GRAY, 2, 0, j2ku_graya_la},
     {"RGBA", OPJ_CLRSPC_SRGB, 3, 1, j2ku_srgb_rgb},
     {"RGBA", OPJ_CLRSPC_SYCC, 3, 1, j2ku_sycc_rgb},
+    {"RGBA", OPJ_CLRSPC_GRAY, 4, 1, j2ku_srgba_rgba},
     {"RGBA", OPJ_CLRSPC_SRGB, 4, 1, j2ku_srgba_rgba},
     {"RGBA", OPJ_CLRSPC_SYCC, 4, 1, j2ku_sycca_rgba},
     {"CMYK", OPJ_CLRSPC_CMYK, 4, 1, j2ku_srgba_rgba},