diff --git a/Tests/test_file_jpeg.py b/Tests/test_file_jpeg.py
index 9f963d80f..0793d6faf 100644
--- a/Tests/test_file_jpeg.py
+++ b/Tests/test_file_jpeg.py
@@ -314,8 +314,6 @@ class TestFileJpeg:
             return layer[0][1:3] + layer[1][1:3] + layer[2][1:3]
 
         # experimental API
-        im = self.roundtrip(hopper(), subsampling=-1)  # default
-        assert getsampling(im) == (2, 2, 1, 1, 1, 1)
         im = self.roundtrip(hopper(), subsampling=0)  # 4:4:4
         assert getsampling(im) == (1, 1, 1, 1, 1, 1)
         im = self.roundtrip(hopper(), subsampling=1)  # 4:2:2
diff --git a/docs/handbook/image-file-formats.rst b/docs/handbook/image-file-formats.rst
index 40db9fe2b..677d10347 100644
--- a/docs/handbook/image-file-formats.rst
+++ b/docs/handbook/image-file-formats.rst
@@ -334,7 +334,8 @@ The :py:meth:`~PIL.Image.Image.save` method supports the following options:
     If present, the image will be stored with the provided raw EXIF data.
 
 **subsampling**
-    If present, sets the subsampling for the encoder.
+    If present, sets the subsampling for the encoder. Otherwise, ``4:2:0`` is
+    the default subsampling.
 
     * ``keep``: Only valid for JPEG files, will retain the original image setting.
     * ``4:4:4``, ``4:2:2``, ``4:2:0``: Specific sampling values
diff --git a/src/PIL/JpegImagePlugin.py b/src/PIL/JpegImagePlugin.py
index 2aa029efb..ae235597f 100644
--- a/src/PIL/JpegImagePlugin.py
+++ b/src/PIL/JpegImagePlugin.py
@@ -618,7 +618,7 @@ def _save(im, fp, filename):
     dpi = [round(x) for x in info.get("dpi", (0, 0))]
 
     quality = info.get("quality", -1)
-    subsampling = info.get("subsampling", -1)
+    subsampling = info.get("subsampling", -2)
     qtables = info.get("qtables")
 
     if quality == "keep":
@@ -628,13 +628,13 @@ def _save(im, fp, filename):
     elif quality in presets:
         preset = presets[quality]
         quality = -1
-        subsampling = preset.get("subsampling", -1)
+        subsampling = preset.get("subsampling", -2)
         qtables = preset.get("quantization")
     elif not isinstance(quality, int):
         raise ValueError("Invalid quality setting")
     else:
         if subsampling in presets:
-            subsampling = presets[subsampling].get("subsampling", -1)
+            subsampling = presets[subsampling].get("subsampling", -2)
         if isinstance(qtables, str) and qtables in presets:
             qtables = presets[qtables].get("quantization")
 
@@ -648,7 +648,7 @@ def _save(im, fp, filename):
         # For compatibility. Before Pillow 4.3, 4:1:1 actually meant 4:2:0.
         # Set 4:2:0 if someone is still using that value.
         subsampling = 2
-    elif subsampling == "keep":
+    elif subsampling == "keep" or subsampling == -1:
         if im.format != "JPEG":
             raise ValueError("Cannot use 'keep' when original image is not a JPEG")
         subsampling = get_sampling(im)