diff --git a/Tests/test_file_ppm.py b/Tests/test_file_ppm.py
index 0a61830a4..fb08d613a 100644
--- a/Tests/test_file_ppm.py
+++ b/Tests/test_file_ppm.py
@@ -95,7 +95,9 @@ def test_16bit_pgm_write(tmp_path: Path) -> None:
     with Image.open("Tests/images/16_bit_binary.pgm") as im:
         filename = str(tmp_path / "temp.pgm")
         im.save(filename, "PPM")
+        assert_image_equal_tofile(im, filename)
 
+        im.convert("I;16").save(filename, "PPM")
         assert_image_equal_tofile(im, filename)
 
 
diff --git a/src/PIL/PpmImagePlugin.py b/src/PIL/PpmImagePlugin.py
index 7bdaa9fe7..8718a5055 100644
--- a/src/PIL/PpmImagePlugin.py
+++ b/src/PIL/PpmImagePlugin.py
@@ -333,7 +333,7 @@ def _save(im: Image.Image, fp: IO[bytes], filename: str | bytes) -> None:
         rawmode, head = "1;I", b"P4"
     elif im.mode == "L":
         rawmode, head = "L", b"P5"
-    elif im.mode == "I":
+    elif im.mode in ("I", "I;16"):
         rawmode, head = "I;16B", b"P5"
     elif im.mode in ("RGB", "RGBA"):
         rawmode, head = "RGB", b"P6"