diff --git a/absl/strings/internal/ostringstream.cc b/absl/strings/internal/ostringstream.cc
index d0f0f84..05324c7 100644
--- a/absl/strings/internal/ostringstream.cc
+++ b/absl/strings/internal/ostringstream.cc
@@ -15,6 +15,7 @@
 #include "absl/strings/internal/ostringstream.h"
 
 namespace absl {
+ABSL_NAMESPACE_BEGIN
 namespace strings_internal {
 
 OStringStream::Buf::int_type OStringStream::overflow(int c) {
@@ -31,4 +32,5 @@
 }
 
 }  // namespace strings_internal
+ABSL_NAMESPACE_END
 }  // namespace absl