diff --git a/ortools/flatzinc/parser_util.cc b/ortools/flatzinc/parser_util.cc
index da43913719..5c08820538 100644
--- a/ortools/flatzinc/parser_util.cc
+++ b/ortools/flatzinc/parser_util.cc
@@ -19,6 +19,7 @@
 #include <string>
 #include <vector>
 
+#include "absl/strings/string_view.h"
 #include "ortools/base/logging.h"
 #include "ortools/base/mathutil.h"
 #include "ortools/base/stl_util.h"
@@ -42,7 +43,7 @@ namespace operations_research {
 namespace fz {
 // Whether the given list of annotations contains the given identifier
 // (or function call).
-bool ContainsId(std::vector<Annotation>* annotations, const std::string& id) {
+bool ContainsId(std::vector<Annotation>* annotations, absl::string_view id) {
   if (annotations != nullptr) {
     for (int i = 0; i < annotations->size(); ++i) {
       if (((*annotations)[i].type == Annotation::IDENTIFIER ||
diff --git a/ortools/glop/revised_simplex.cc b/ortools/glop/revised_simplex.cc
index bc019b7beb..eb3d430324 100644
--- a/ortools/glop/revised_simplex.cc
+++ b/ortools/glop/revised_simplex.cc
@@ -25,6 +25,7 @@
 
 #include "absl/strings/str_cat.h"
 #include "absl/strings/str_format.h"
+#include "absl/strings/string_view.h"
 #include "ortools/base/commandlineflags.h"
 #include "ortools/base/logging.h"
 #include "ortools/base/strong_vector.h"
@@ -3701,7 +3702,7 @@ void RevisedSimplex::DisplayErrors() {
 namespace {
 
 std::string StringifyMonomialWithFlags(const Fractional a,
-                                       const std::string& x) {
+                                       absl::string_view x) {
   return StringifyMonomial(
       a, x, absl::GetFlag(FLAGS_simplex_display_numbers_as_fractions));
 }