diff --git a/test/unittest/documenttest.cpp b/test/unittest/documenttest.cpp
index 940b2958..2ee6b103 100644
--- a/test/unittest/documenttest.cpp
+++ b/test/unittest/documenttest.cpp
@@ -241,7 +241,7 @@ TEST(Document, UserBuffer) {
     char parseBuffer[1024];
     MemoryPoolAllocator<> valueAllocator(valueBuffer, sizeof(valueBuffer));
     MemoryPoolAllocator<> parseAllocator(parseBuffer, sizeof(parseBuffer));
-    DocumentType doc(&valueAllocator, sizeof(parseBuffer), &parseAllocator);
+    DocumentType doc(&valueAllocator, sizeof(parseBuffer) / 2, &parseAllocator);
     doc.Parse(" { \"hello\" : \"world\", \"t\" : true , \"f\" : false, \"n\": null, \"i\":123, \"pi\": 3.1416, \"a\":[1, 2, 3, 4] } ");
     EXPECT_FALSE(doc.HasParseError());
     EXPECT_LE(valueAllocator.Size(), sizeof(valueBuffer));