diff --git a/python/_brotli.cc b/python/_brotli.cc
index a6f925e..5e1828e 100644
--- a/python/_brotli.cc
+++ b/python/_brotli.cc
@@ -414,7 +414,7 @@ static BROTLI_BOOL decompress_stream(BrotliDecoderState* dec,
       (*output).insert((*output).end(), buffer, buffer + buffer_length);
     }
   }
-  ok = result != BROTLI_DECODER_RESULT_ERROR;
+  ok = result != BROTLI_DECODER_RESULT_ERROR && !available_in;
 
   Py_END_ALLOW_THREADS
   return ok;
@@ -672,7 +672,7 @@ static PyObject* brotli_decompress(PyObject *self, PyObject *args, PyObject *key
     if (available_out != 0)
       output.insert(output.end(), next_out, next_out + available_out);
   }
-  ok = result == BROTLI_DECODER_RESULT_SUCCESS;
+  ok = result == BROTLI_DECODER_RESULT_SUCCESS && !available_in;
   BrotliDecoderDestroyInstance(state);
 
   Py_END_ALLOW_THREADS
diff --git a/python/tests/decompress_test.py b/python/tests/decompress_test.py
index 7a9e9e3..814e563 100644
--- a/python/tests/decompress_test.py
+++ b/python/tests/decompress_test.py
@@ -31,6 +31,10 @@ class TestDecompress(_test_utils.TestCase):
         self._decompress(test_data)
         self._check_decompression(test_data)
 
+    def test_garbage_appended(self):
+        with self.assertRaises(brotli.error):
+            brotli.decompress(brotli.compress(b'a') + b'a')
+
 
 _test_utils.generate_test_methods(TestDecompress, for_decompression=True)
 
diff --git a/python/tests/decompressor_test.py b/python/tests/decompressor_test.py
index 99667bc..05918ad 100644
--- a/python/tests/decompressor_test.py
+++ b/python/tests/decompressor_test.py
@@ -43,6 +43,15 @@ class TestDecompressor(_test_utils.TestCase):
         self._decompress(test_data)
         self._check_decompression(test_data)
 
+    def test_garbage_appended(self):
+        with self.assertRaises(brotli.error):
+            self.decompressor.process(brotli.compress(b'a') + b'a')
+
+    def test_already_finished(self):
+        self.decompressor.process(brotli.compress(b'a'))
+        with self.assertRaises(brotli.error):
+            self.decompressor.process(b'a')
+
 
 _test_utils.generate_test_methods(TestDecompressor, for_decompression=True)