diff --git a/flang/runtime/unit.cpp b/flang/runtime/unit.cpp
--- a/flang/runtime/unit.cpp
+++ b/flang/runtime/unit.cpp
@@ -114,6 +114,7 @@
     // Otherwise, OPEN on open unit with new FILE= implies CLOSE
     DoImpliedEndfile(handler);
     FlushOutput(handler);
+    TruncateFrame(0, handler);
     Close(CloseStatus::Keep, handler);
   }
   if (newPath.get() && newPathLength > 0) {