diff --git a/src/PIL/TiffImagePlugin.py b/src/PIL/TiffImagePlugin.py
index 17f456930..fed10332c 100644
--- a/src/PIL/TiffImagePlugin.py
+++ b/src/PIL/TiffImagePlugin.py
@@ -1826,6 +1826,6 @@ Image.register_open(TiffImageFile.format, TiffImageFile, _accept)
 Image.register_save(TiffImageFile.format, _save)
 Image.register_save_all(TiffImageFile.format, _save_all)
 
-Image.register_extensions(TiffImageFile.format, [".tif", ".tiff"])
+Image.register_extension(TiffImageFile.format, [".tif", ".tiff"])
 
 Image.register_mime(TiffImageFile.format, "image/tiff")