diff --git a/src/PIL/ImageFile.py b/src/PIL/ImageFile.py
index 1c2c06aa3..99cb7ec37 100644
--- a/src/PIL/ImageFile.py
+++ b/src/PIL/ImageFile.py
@@ -751,7 +751,7 @@ class Exif(MutableMapping):
             self._data[0x8825] = ifd
             self._ifds[0x8825] = ifd
 
-    def toBytes(self, offset=0):
+    def tobytes(self, offset=0):
         from . import TiffImagePlugin
         if self.endian == "<":
             head = b"II\x2A\x00\x08\x00\x00\x00"
@@ -760,7 +760,7 @@ class Exif(MutableMapping):
         ifd = TiffImagePlugin.ImageFileDirectory_v2(ifh=head)
         for tag, value in self._data.items():
             ifd[tag] = value
-        return b"Exif\x00\x00"+head+ifd.toBytes(offset)
+        return b"Exif\x00\x00"+head+ifd.tobytes(offset)
 
     def get_ifd(self, tag):
         if tag not in self._ifds and tag in self._data:
diff --git a/src/PIL/JpegImagePlugin.py b/src/PIL/JpegImagePlugin.py
index 0f50ff352..946006c75 100644
--- a/src/PIL/JpegImagePlugin.py
+++ b/src/PIL/JpegImagePlugin.py
@@ -726,7 +726,7 @@ def _save(im, fp, filename):
 
     exif = info.get("exif", b"")
     if isinstance(exif, ImageFile.Exif):
-        exif = exif.toBytes()
+        exif = exif.tobytes()
 
     # get keyword arguments
     im.encoderconfig = (
diff --git a/src/PIL/PngImagePlugin.py b/src/PIL/PngImagePlugin.py
index 9aea1f059..588cee02f 100644
--- a/src/PIL/PngImagePlugin.py
+++ b/src/PIL/PngImagePlugin.py
@@ -887,7 +887,7 @@ def _save(im, fp, filename, chunk=putchunk):
     exif = im.encoderinfo.get("exif", im.info.get("exif"))
     if exif:
         if isinstance(exif, ImageFile.Exif):
-            exif = exif.toBytes(8)
+            exif = exif.tobytes(8)
         if exif.startswith(b"Exif\x00\x00"):
             exif = exif[6:]
         chunk(fp, b"eXIf", exif)
diff --git a/src/PIL/TiffImagePlugin.py b/src/PIL/TiffImagePlugin.py
index 2c703e32c..77688e56b 100644
--- a/src/PIL/TiffImagePlugin.py
+++ b/src/PIL/TiffImagePlugin.py
@@ -785,7 +785,7 @@ class ImageFileDirectory_v2(MutableMapping):
             warnings.warn(str(msg))
             return
 
-    def toBytes(self, offset=0):
+    def tobytes(self, offset=0):
         # FIXME What about tagdata?
         result = self._pack("H", len(self._tags_v2))
 
@@ -859,7 +859,7 @@ class ImageFileDirectory_v2(MutableMapping):
             fp.write(self._prefix + self._pack("HL", 42, 8))
 
         offset = fp.tell()
-        result = self.toBytes(offset)
+        result = self.tobytes(offset)
         fp.write(result)
         return offset + len(result)
 
diff --git a/src/PIL/WebPImagePlugin.py b/src/PIL/WebPImagePlugin.py
index 6b85da254..4a11a18c1 100644
--- a/src/PIL/WebPImagePlugin.py
+++ b/src/PIL/WebPImagePlugin.py
@@ -218,7 +218,7 @@ def _save_all(im, fp, filename):
     icc_profile = im.encoderinfo.get("icc_profile", "")
     exif = im.encoderinfo.get("exif", "")
     if isinstance(exif, ImageFile.Exif):
-        exif = exif.toBytes()
+        exif = exif.tobytes()
     xmp = im.encoderinfo.get("xmp", "")
     if allow_mixed:
         lossless = False
@@ -319,7 +319,7 @@ def _save(im, fp, filename):
     icc_profile = im.encoderinfo.get("icc_profile", "")
     exif = im.encoderinfo.get("exif", "")
     if isinstance(exif, ImageFile.Exif):
-        exif = exif.toBytes()
+        exif = exif.tobytes()
     xmp = im.encoderinfo.get("xmp", "")
 
     if im.mode not in _VALID_WEBP_LEGACY_MODES: