diff --git a/tests/mbconv/mbconvtest.cpp b/tests/mbconv/mbconvtest.cpp
index 5c6fa443ed..d7bf61745c 100644
--- a/tests/mbconv/mbconvtest.cpp
+++ b/tests/mbconv/mbconvtest.cpp
@@ -1040,7 +1040,7 @@ void MBConvTestCase::TestStreamEncoder(
     {
         textOutputStream.PutChar( wideBuffer[i] );
     }
-    CPPUNIT_ASSERT( memoryOutputStream.TellO() == multiBytes );
+    CPPUNIT_ASSERT_EQUAL( (wxFileOffset)multiBytes, memoryOutputStream.TellO() );
     wxCharBuffer copy( memoryOutputStream.TellO() );
     memoryOutputStream.CopyTo( copy.data(), memoryOutputStream.TellO());
     CPPUNIT_ASSERT( 0 == memcmp( copy.data(), multiBuffer, multiBytes ) );