diff --git a/src/core/IronPython.Modules/zlib/zlib.net/InfTree.cs b/src/core/IronPython.Modules/zlib/zlib.net/InfTree.cs
index 3a0be26d6..f0c21f56a 100644
--- a/src/core/IronPython.Modules/zlib/zlib.net/InfTree.cs
+++ b/src/core/IronPython.Modules/zlib/zlib.net/InfTree.cs
@@ -312,7 +312,7 @@ internal static int inflate_trees_bits(int[] c, int[] bb, int[] tb, int[] hp, ZS
 			{
 				z.msg = "oversubscribed dynamic bit lengths tree";
 			}
-			else if (r == (int)ZLibResultCode.Z_DATA_ERROR || bb[0] == 0)
+			else if (r == (int)ZLibResultCode.Z_BUF_ERROR || bb[0] == 0)
 			{
 				z.msg = "incomplete dynamic bit lengths tree";
 				r = (int)ZLibResultCode.Z_DATA_ERROR;
diff --git a/tests/suite/modules/misc/test_zlib.py b/tests/suite/modules/misc/test_zlib.py
index 0a063537e..fcb928fc5 100644
--- a/tests/suite/modules/misc/test_zlib.py
+++ b/tests/suite/modules/misc/test_zlib.py
@@ -76,6 +76,16 @@ def test_deflate(self):
         self.assertEqual(do.decompress(self.deflate_data), self.text)
         self.assertEqual(zlib.decompress(self.deflate_data, -zlib.MAX_WBITS), self.text)
 
+    def test_invalid_bit_length_trees(self):
+        # These dynamic blocks have incomplete and oversubscribed code-length alphabets.
+        for data in (b'\x05\x00\x00\x01', b'\x05\x00\x92\x00'):
+            with self.subTest(data=data, api='decompress'):
+                with self.assertRaisesRegex(zlib.error, r'Error -3\b'):
+                    zlib.decompress(data, -zlib.MAX_WBITS)
+            with self.subTest(data=data, api='decompressobj'):
+                with self.assertRaisesRegex(zlib.error, r'Error -3\b'):
+                    zlib.decompressobj(-zlib.MAX_WBITS).decompress(data)
+
     def test_gzip_stream(self):
         """gzip header, uncomplete header"""
         for delta in range(1, 25):