diff --git a/tpie/sort_manager.h b/tpie/sort_manager.h
index e34da0cc9..ffe780e0e 100644
--- a/tpie/sort_manager.h
+++ b/tpie/sort_manager.h
@@ -710,7 +710,7 @@ void sort_manager<T,I,M>::merge_to_output(progress_indicator_base* indicator, tp
 			stream->seek(0);
 		}
 
-		stream_size_type check_size=0;
+		TPIE_OS_OFFSET check_size=0;
 		// For each new output stream, fill with merged runs.
 		// strange indexing is for the case that there are fewer than mrgArity
 		// output streams needed, and we use the LAST nOutputStreams. This
@@ -798,7 +798,7 @@ void sort_manager<T,I,M>::merge_to_output(progress_indicator_base* indicator, tp
 				 outStream, -1, indicator);
 
 	if (indicator) indicator->done();
-	tp_assert(outStream->size() == nInputItems, "item count mismatch");
+	tp_assert((TPIE_OS_OFFSET)outStream->size() == nInputItems, "item count mismatch");
 
 	TP_LOG_DEBUG("merge cleanup\n");