try to fix windows compile

1 files changed, 1 insertions, 1 deletions

diff --git a/src/mongo/db/pipeline/document_source_unwind.cpp b/src/mongo/db/pipeline/document_source_unwind.cpp
index f32ccc69a77..d1488887cbd 100755
--- a/src/mongo/db/pipeline/document_source_unwind.cpp
+++ b/src/mongo/db/pipeline/document_source_unwind.cpp
@@ -94,7 +94,7 @@ namespace mongo {
         }
 
         // The target field must be an array to unwind.
-        uassert(15978, str::stream() << DocumentSourceUnwind::unwindName
+        uassert(15978, str::stream() << (string)DocumentSourceUnwind::unwindName
                 << ":  value at end of field path must be an array",
                 pathValue->getType() == Array);