diff --git a/tensorflow/core/grappler/optimizers/graph_optimizer_stage.cc b/tensorflow/core/grappler/optimizers/graph_optimizer_stage.cc
index f584b8d1548..8c2619529f6 100644
--- a/tensorflow/core/grappler/optimizers/graph_optimizer_stage.cc
+++ b/tensorflow/core/grappler/optimizers/graph_optimizer_stage.cc
@@ -20,7 +20,7 @@ namespace tensorflow {
 namespace grappler {
 
 const NodeScopeAndName ParseNodeScopeAndName(const string& node_name) {
-  auto pos = node_name.find_last_of("/");
+  auto pos = node_name.find_last_of('/');
   if (pos == string::npos) {
     return {"", node_name};
   } else {
diff --git a/tensorflow/core/grappler/optimizers/scoped_allocator_optimizer.cc b/tensorflow/core/grappler/optimizers/scoped_allocator_optimizer.cc
index 11f95894ff9..cf601c98acd 100644
--- a/tensorflow/core/grappler/optimizers/scoped_allocator_optimizer.cc
+++ b/tensorflow/core/grappler/optimizers/scoped_allocator_optimizer.cc
@@ -48,13 +48,13 @@ const char kScopedAllocatorAttrName[] = "_scoped_allocator";
 // matches op_name, i.e. it looks from the name like this node is
 // of that op type.
 bool HasOpName(const string& node_name, const string& op_name) {
-  size_t begin = node_name.rfind("/");
+  size_t begin = node_name.rfind('/');
   if (begin == string::npos) {
     begin = 0;
   } else {
     ++begin;
   }
-  size_t end = node_name.rfind("_");
+  size_t end = node_name.rfind('_');
   if (end != string::npos) {
     size_t p = end + 1;
     while (p < node_name.size()) {