diff --git a/internal/ceres/line_search.cc b/internal/ceres/line_search.cc
index c3f0213..a396691 100644
--- a/internal/ceres/line_search.cc
+++ b/internal/ceres/line_search.cc
@@ -67,15 +67,17 @@
   return sample;
 };
 
+}  // namespace
+
+
+std::ostream& operator<<(std::ostream &os, const FunctionSample& sample);
+
 // Convenience stream operator for pushing FunctionSamples into log messages.
-std::ostream& operator<<(std::ostream &os,
-                         const FunctionSample& sample) {
+std::ostream& operator<<(std::ostream &os, const FunctionSample& sample) {
   os << sample.ToDebugString();
   return os;
 }
 
-}  // namespace
-
 LineSearch::LineSearch(const LineSearch::Options& options)
     : options_(options) {}