diff -r 5fea362b92fc Lib/test/test_zipfile.py
--- a/Lib/test/test_zipfile.py	Wed Apr 25 19:45:11 2012 +0200
+++ b/Lib/test/test_zipfile.py	Sun Apr 29 16:12:14 2012 +0300
@@ -920,6 +920,22 @@
         caught."""
         self.assertRaises(RuntimeError, zipfile.ZipFile, TESTFN, "w", -1)
 
+    zip_with_unsupported_compression = (
+        b'PK\x03\x04\n\x03\x00\x00\x124\x02{\x9d@2\xd1'
+        b'Mx\x04\x00\x00\x00\x04\x00\x00\x00\x04\x00\x00\x00te'
+        b'stTestPK\x01\x02\x14\x03\n\x03\x00\x00'
+        b'\x124\x02{\x9d@2\xd1Mx\x04\x00\x00\x00\x04\x00'
+        b'\x00\x00\x04\x00\x00\x00\x00\x00\x00\x00\x00\x00 \x80\xa4\x81'
+        b'\x00\x00\x00\x00testPK\x05\x06\x00\x00\x00\x00'
+        b'\x01\x00\x01\x002\x00\x00\x00&\x00\x00\x00\x00\x00')
+
+    def test_unsupported_compression(self):
+        """Check that attempting to call open() for an item that compressed
+        with unsupported compression type raises a RuntimeError."""
+        zipdata = self.zip_with_unsupported_compression
+        with zipfile.ZipFile(io.BytesIO(zipdata), mode="r") as zipf:
+            self.assertRaises(RuntimeError, zipf.open, "test", "r")
+
     def test_null_byte_in_filename(self):
         """Check that a filename containing a null byte is properly
         terminated."""
diff -r 5fea362b92fc Lib/zipfile.py
--- a/Lib/zipfile.py	Wed Apr 25 19:45:11 2012 +0200
+++ b/Lib/zipfile.py	Sun Apr 29 16:12:14 2012 +0300
@@ -487,6 +487,8 @@
 
         if self._compress_type == ZIP_DEFLATED:
             self._decompressor = zlib.decompressobj(-15)
+        elif self._compress_type != ZIP_STORED:
+            raise RuntimeError("Compression method %d is not supported" % self._compress_type)
         self._unconsumed = b''
 
         self._readbuffer = b''