diff --git a/util/__init__.py b/util/__init__.py
index e823efea..037b0d8a 100644
--- a/util/__init__.py
+++ b/util/__init__.py
@@ -196,9 +196,11 @@ def unzstd(contents):
     """ unzstd contents in memory and return the data
     """
     try:
-        if hasattr(zstd, 'decompress'):
-            return zstd.decompress(contents)
-        return zstd.ZstdDecompressor().stream_reader(contents).read()
+        if zstd.__name__ == 'zstandard':
+            # zstandard.decompress() fails without a content size in the frame
+            # header and stops after the first frame, so stream instead
+            return zstd.ZstdDecompressor().stream_reader(contents, read_across_frames=True).read()
+        return zstd.decompress(contents)
     except (zstd.ZstdError, Exception) as e:
         error_message(text=f'zstd: {e}')
 
diff --git a/util/tests/test_utils.py b/util/tests/test_utils.py
index 4205150f..23735348 100644
--- a/util/tests/test_utils.py
+++ b/util/tests/test_utils.py
@@ -17,6 +17,7 @@
 import gzip
 import hashlib
 from io import BytesIO
+from unittest import skipIf
 from unittest.mock import MagicMock
 
 from django.test import TestCase, override_settings
@@ -24,9 +25,14 @@
 from util import (
     Checksum, bunzip2, extract, get_checksum, get_md5, get_sha1, get_sha256,
     get_sha512, gunzip, has_setting_of_type, is_epoch_time, response_is_valid,
-    sanitize_filter_params, tz_aware_datetime,
+    sanitize_filter_params, tz_aware_datetime, unzstd,
 )
 
+try:
+    import zstandard
+except ImportError:
+    zstandard = None
+
 
 @override_settings(
     CELERY_TASK_ALWAYS_EAGER=True,
@@ -138,6 +144,20 @@ def test_extract_gzip(self):
         result = extract(compressed, 'gz')
         self.assertEqual(result, original)
 
+    @skipIf(zstandard is None, 'zstandard not installed')
+    def test_unzstd_without_content_size(self):
+        """Test unzstd with a frame that does not declare its content size."""
+        original = b'x' * 100000
+        compressed = zstandard.ZstdCompressor(write_content_size=False).compress(original)
+        self.assertEqual(unzstd(compressed), original)
+
+    @skipIf(zstandard is None, 'zstandard not installed')
+    def test_extract_zstd_multiple_frames(self):
+        """Test extract with zstd data made of multiple frames."""
+        first, second = b'a' * 50000, b'b' * 50000
+        compressed = zstandard.ZstdCompressor().compress(first) + zstandard.ZstdCompressor().compress(second)
+        self.assertEqual(extract(compressed, 'zst'), first + second)
+
     def test_extract_unknown_format(self):
         """Test extract with unknown format returns original."""
         data = b'unchanged data'