diff --git a/CHANGELOG.md b/CHANGELOG.md
index c6dfaf8a8..cf359236c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,6 +12,7 @@
 - Better ignore tiff directories that aren't part of the pyramid ([943](../../pull/943))
 - Fix an issue with styling frames in ome tiffs ([945](../../pull/945))
 - Better handle large user records in annotation elements ([949](../../pull/949))
+- Harden which output formats are supported ([950](../../pull/950))
 
 ### Changes
 - Adjusted rest request logging rates for region endpoint ([948](../../pull/948))
diff --git a/large_image/tilesource/utilities.py b/large_image/tilesource/utilities.py
index c134ea08d..9f19f021c 100644
--- a/large_image/tilesource/utilities.py
+++ b/large_image/tilesource/utilities.py
@@ -99,7 +99,19 @@ def _encodeImageBinary(image, encoding, jpegQuality, jpegSubsampling, tiffCompre
     elif encoding == 'PNG':
         params['compress_level'] = 2
     output = io.BytesIO()
-    image.save(output, encoding, **params)
+    try:
+        image.save(output, encoding, **params)
+    except Exception:
+        retry = True
+        if image.mode not in {'RGB', 'L'}:
+            image = image.convert('RGB')
+            try:
+                image.convert('RGB').save(output, encoding, **params)
+                retry = False
+            except Exception:
+                pass
+        if retry:
+            image.convert('1').save(output, encoding, **params)
     return ImageBytes(
         output.getvalue(),
         mimetype=f'image/{encoding.lower().replace("tiled", "tiff")}'
@@ -931,6 +943,10 @@ def addPILFormatsToOutputOptions():
     # Call this to actual register the extensions
     PIL.Image.registered_extensions()
     for key, value in PIL.Image.MIME.items():
+        # We don't support these formats; ICNS and ICO have fixed sizes; PALM
+        # and PDF can't be read back by PIL without extensions
+        if key in {'ICNS', 'ICO', 'PALM', 'PDF'}:
+            continue
         if key not in TileOutputMimeTypes and key in PIL.Image.SAVE:
             TileOutputMimeTypes[key] = value
     for key, value in PIL.Image.registered_extensions().items():
diff --git a/test/test_source_base.py b/test/test_source_base.py
index 7270ab8f6..a7a1366e4 100644
--- a/test/test_source_base.py
+++ b/test/test_source_base.py
@@ -1,8 +1,10 @@
+import io
 import os
 import re
 import sys
 from pathlib import Path
 
+import PIL.Image
 import pytest
 
 import large_image
@@ -540,3 +542,24 @@ def testImageBytes():
     assert 'ImageBytes' in repr(ib)
     assert ib._repr_jpeg_() is None
     assert ib._repr_png_() is None
+
+
+@pytest.mark.parametrize('format', [
+    format for format in large_image.constants.TileOutputMimeTypes
+    if format not in {'TILED'}])
+def testOutputFormats(format):
+    imagePath = datastore.fetch('sample_image.ptif')
+    testDir = os.path.dirname(os.path.realpath(__file__))
+    imagePathRGBA = os.path.join(testDir, 'test_files', 'rgba_geotiff.tiff')
+
+    ts = large_image.open(imagePath, encoding=format)
+    img = PIL.Image.open(io.BytesIO(ts.getTile(0, 0, 0)))
+    assert (img.width, img.height) == (256, 256)
+    img = PIL.Image.open(io.BytesIO(ts.getThumbnail(encoding=format)[0]))
+    assert (img.width, img.height) == (256, 53)
+
+    ts = large_image.open(imagePathRGBA, encoding=format)
+    img = PIL.Image.open(io.BytesIO(ts.getTile(0, 0, 0)))
+    assert (img.width, img.height) == (256, 256)
+    img = PIL.Image.open(io.BytesIO(ts.getThumbnail(encoding=format)[0]))
+    assert (img.width, img.height) == (256, 256)