diff --git a/taglib/toolkit/tbytevectorstream.cpp b/taglib/toolkit/tbytevectorstream.cpp
index a01da552..dc480a26 100644
--- a/taglib/toolkit/tbytevectorstream.cpp
+++ b/taglib/toolkit/tbytevectorstream.cpp
@@ -81,7 +81,7 @@ ByteVector ByteVectorStream::readBlock(ulong length)
 void ByteVectorStream::writeBlock(const ByteVector &data)
 {
   uint size = data.size();
-  if(d->position + size > length()) {
+  if(long(d->position + size) > length()) {
     truncate(d->position + size);
   }
   memcpy(d->data.data() + d->position, data.data(), size);