diff --git a/test/ParallelIOTest.cpp b/test/ParallelIOTest.cpp
index ed7291e3be..a9008be057 100644
--- a/test/ParallelIOTest.cpp
+++ b/test/ParallelIOTest.cpp
@@ -85,6 +85,7 @@ void write_test_zero_extent( bool fileBased, std::string file_ending, bool write
         e["position"]["x"].storeChunk(position_local, {offset}, {rank});
         e["positionOffset"]["x"].storeChunk(positionOffset_local, {offset}, {rank});
     }
+    o.flush();
 
     //TODO read back, verify
 }