diff --git a/clang/lib/Frontend/FrontendAction.cpp b/clang/lib/Frontend/FrontendAction.cpp
index 1d82fc775b28a..cf081830c95bb 100644
--- a/clang/lib/Frontend/FrontendAction.cpp
+++ b/clang/lib/Frontend/FrontendAction.cpp
@@ -226,6 +226,8 @@ class DeserializedDeclsSourceRangePrinter : public ASTConsumer,
     }
     *OS << "  ]\n";
     *OS << "}\n";
+
+    OS->flush();
   }
 };