diff --git a/internal/ceres/test_util.cc b/internal/ceres/test_util.cc
index a3f67bd..8af48ab 100644
--- a/internal/ceres/test_util.cc
+++ b/internal/ceres/test_util.cc
@@ -30,6 +30,7 @@
 //
 // Utility functions useful for testing.
 
+#include <algorithm>
 #include <cmath>
 #include "ceres/file.h"
 #include "ceres/stringprintf.h"